Many of the Vicksburg prisoners were exchanged as early as September, 1863, while in parole camps.

Some of the Trans Miss units were not exchanged until 1864.

The Offical Records has extensive dialogue regarding the controversy over this excahnge, in particular, Series II, Vol VI.

A search at the on line site for the Official records will provide links on the subject:

http://ehistory.osu.edu/osu/search/searchMore.cfm?more=1&typeOfSearch=or&keywords=vicksburg%20prisoners

And, we have some extremely knowledgeable posters [as you have already seen with the responses by Bryan & Doyle] on these boards that have furnished pertinent information regarding the exchange. A search on these boads will reveal a tremendous amount of information, such as:

Posted By: Hugh Simmons
Date: Thursday, 13 May 2004, at 7:48 a.m.
In Response To: vicksburg (Cump Turchin)
The able bodied Confederate soldiers released on parole at Vicksburg walked out of Vicksburg on July 11th. The last point of Federal control was the Big Black River Bridge. Federal authorities refused to let them march out of Vicksburg in their military formations as the Confederate commanders had requested. General Grant's hope was that most of these parolees would go home and drop out of the war. Many did just that.
Some small number (as I remember about 1,000) of the captured Confederates refused to accept a release on parole because they did not wish to return to duty with the Confederate army. These men were eventually sent north to Camp Morton and held as prisoners of war.
After Big Black Bridge, the parolees were on their own. Confederate authorities tried to get the men into a parole camp at Enterprise, Mississippi but had very limited success. Most parolees were determined not to be held in a parole camp awaiting exchange by their own army. Many of these would (and did) willingly return when they believed that an exchange was imminent which would release them from their individual parole obligations and allow them to return to duty.
However, because most of the men went home first, those who did report immediately to parole camp were granted 30 day furloughs. Many of those who went home first later reported into various parole camps and were declared exchanged. As I recall, the correspondence indicates that men from specific units (perhaps by state) were to report specifically to either Enterprise, Mississippi or Demopolis, Alabama upon returning from furlough. You can find this in the OR, Series II, Volume VI.
I have not specifically studied the Georgia regiments which were released on parole at Vicksburg, but can give you some background. The Georgia units you named composed Barton's Brigade in Major General Carter L. Stevenson's Division at Vicksburg. On September 12, 1863, Confederate authorities declared exchanged those men of Major General Carter L. Stevenson's division who had reported into parole camp to be ready for exchange. [See Exchange Notice No. 6 in the Official Records, Series II, Volume VI, page 295.]
The wording suggests that all men of Stevenson's division were declared exchanged, but I don't think that is what is meant. Exchange was an accounting process in which named individual prisoners were swapped one-for-one (or multiple equivalents from a table of exchange as provided in the Dix-Hill Cartel of July 1862) and the Confederates were smart enough to declare exchanged only able bodied men present in camp who were ready and willing to return to duty.
The Confederates declared these men exchanged against a stack of "paroles in the field" which had been accumulated in Richmond. These were from captured Federal soldiers who had been paroled and released at or near their place of capture and the parole certificate sent to Richmond for a future exchange accounting. When Colonel Ould ran out of "paroles in the field" those Vicksburg and Port Hudson parolees who had gone home to the Trans-Mississippi were stranded. They were not exchanged until August 1864 under a special agreement in the Trans-Mississippi. The Federals cried "foul" over the "paroles in the field" interpretation of the Dix-Hill Cartel by the Confederates in the summer and fall of 1863 and this was the final straw in the collapse of the exchange agreement.

Posted By: Bryan Howerton
Date: Friday, 24 September 2004, at 5:17 p.m.
In Response To: Re: 3rd Ark Deserter John Turner (Doug Bright)
One thing to keep in mind is that about the time the Vicksburg and Port Hudson prisoners were being exchanged, we reach the last of the surviving muster rolls for most Arkansas regiments in the Trans-Mississippi Department. Anecdotal accounts indicate that many, if not most, of the exchanged prisoners appear to have continued to serve, but this can only proven on an individual basis if the soldier left footprints in subsequent prisoner-of-war records, casualty lists, quartermaster receipts, parole lists, pension records, letters, diaries, etc.
If I wasn't so obsessive about documenting things, I would almost go so far as to say that it can be assumed that a soldier served after being exchanged unless proven differently. But, I like to have all the boxes checked, so I have to take the opposite position, even though I "know" in my gut that the soldier probably served after being exchanged.

Posted By: Bryan Howerton
Date: Thursday, 9 October 2003, at 8:36 p.m.
In Response To: 15th N/W Ark. Inf. Regt. (E.S. Milton)
The Vicksburg and Port Hudson regiments were exchanged back in Arkansas by December 1863, where most of them were soon consolidated into three regiments. There are no muster rolls for any of these regiments that I know of which date later than February 28, 1863, in most cases, and April 30, 1863, in a couple of cases. The last muster roll for the 15th Northwest Arkansas Regiment was dated February 28, 1863, while stationed at Camp Donelson, Mississippi

Posted By: Danny Odom
Date: Friday, 10 October 2003, at 7:49 a.m.
In Response To: Re:(Bryan Howerton)
Bryan, How does the timeline for these 3 consolidated regiments compare to Dockery's brigade of exchanged regiments? It also appears that some of Dockery's men were unable to obtain mounts, and were formed into some type of provisional infantry unit. Did all 3 of these organizations coexist for some period of time?
Confused as usual.
Danny, that's the group I was referring to. The 1st, 2nd and 3rd Arkansas Consolidated Regiments. The Vicksburg and Port Hudson regiments started gathering back in Arkansas beginning in September 1863, and by December the last of them were declared exchanged. They were consolidated into the three regiments we're talking about, and became mounted infantry (most of them). Somewhere around here I have the date of consolidation and reorganization, and a breakdown of which regiments were consolidated into each of the three new mounted regiments. I'll post it as soon as I can find it.
Bryan

Posted By: Keenan Williams
Date: Saturday, 11 October 2003, at 9:18 p.m.
In Response To: Re: 15th N/W Ark. Inf. Regt. (Danny Odom)
Dockery's exhange camp is described by Charlene Moss Williams as being on her father's farm. "It was situated three miles from Washington on the old Military Road as it runs from Washington to Fulton"
She describes in OLD TOWN SPEAKS a ball honoring Col Robert Crockett (grandson of David) at the home complete with orchestra. Present besides Dockery and his staff were Price, Fagan, Col. Dan Jones, Haynes Williams, and Col Elias Boudinot.

Posted By: Bryan Howerton
Date: Wednesday, 9 February 2005, at 11:58 p.m.
In Response To: 20th Arkansas Inf. (Brett Quillin)
After being exchanged, those units were consolidated in the Trans-Mississippi Department, and had no further independent existence. The men continued to serve under the designation of the 3rd Arkansas Consolidated Regiment, but there are no muster rolls or other records. The 12th Arkansas Battalion served for a short period as mounted infantry before being consolidated.

Posted By: Allan Richard
Date: Monday, 18 July 2005, at 8:55 a.m.
In Response To: Re: Louisiana 26th Infantry (Danny Odom)
The LA units paroled at Vicksburg and Port Hudson were not exchanged until August 1864, over a year after their parole. From what I could find they all appeared to have been exchanged at the same time. There is a lot of confusion about the exchange and Kirby Smith issued orders saying they were exchange several months before it actually happened.
Thomas’ brigade was actually H. W. Allen’s brigade, when he got back to LA from Richmond and found out he had been elected Governor the brigade went to Thomas.
We actually explore the theory that a number of the veterans of Vicksburg and Port Hudson broke parole to fight in the battle of Sabine Crossroads and Pleasant Hill in our book. There is no hard evidence but there is some good circumstantial evidence.