I have found evidence that CS deserters/POWs were actively recruited into US units. The practice was frowned upon by by General Grant and others but was approved by Lincoln "with a wink and a nod". At Camp Morton, Indiana at least 100 POWs taken from Vaughn's Brigade at Big Black River, Mississippi, were enlisted into what became Co A 8th Tennessee Cavalry and returned to Tennessee to fight against their former tentmates on several occasions. There seems to be another catagory as well, those allowed into to Indiana and other units. I suspect those likely had kinsmen in those units. My friend Hugh Simmons suggested that this practice was encouraged by Union Governors to ease pressure on recruiting/conscription efforts on local voters.