Cornell university has the official records of the union and confederate armies in the civil war online. this might not be news to most of you but it may be helpful to some. It has info on some of the activity of this unit (skirmishes at saint andrews,tunica,bayou sara, pollard...)
the site is http://cdl.library.cornell.edu/moa/moa_browse.html

under searches use proximity search- type in words like 15th confederate cavalry, fifteenth confederate cavalry, maury (for col. maury), tunica, pine barren bridge.

There are details for the each company before and after they became part of the regiment.

Co. B (marianna dragoons) before becoming part of the regiment had a skirmish at st. andrews bay in present day panama city. A search using the words saint andrews bay and marianna dragoons will bring this up. The Union perspective of the skirmish can also be found on the naval records provided by cornell (list those killed and wounded)

If anyone has any other info on this regt specifically co. b it would be greatly appreciated.