Hi B17, normally, Spits (or other aircraft) captured by the Luftwaffe would be more or less intact, probably having belly-landed or force-landed in an occupied country. They would, if required, recover the A/C from the landing site and repair them to flying status, just as the R.A.F., via Farnborough etc., did with captured Axis aircraft in Britain. Those allied aircraft that were too badly damaged would be scrapped and re-cycled.
Makes you think, I wonder how many pieces of what were once Mustangs or Spits, for instance, became Messerschmitts or Focke Wulfs that shot down more Mustangs and Spits that became more.......?