According to individual soldier listings on Mr Gerdes' website, captured men served various capacities, such as:
Captured Jan 28 1865 Bradley Co.
Second Arkansas Cavalry Batallion, CSA Company B - Bradley County Troop,
Hayes' Regiment,
2nd Arkansas Infantry Regiment Confederate States of America Company G,
6th (Monroe's) Arkansas Cavalry Company G,
Captured Jan 27 1865; Bradley Co.
Rollin's AR Bn Conscripts
26 Arkansas Infantry Company F
These are the examples I've found to date - there may be more instances. Thanks for any clues!