Hello
i don't know about german army but there was Finland pl37. Finlanders captured 1 or 2 PL37 during "winter war" , restored it and use during the end of war as anti aircraft. it's in the museum now. there is some picture of it .
captured by fins L37
Probably german army couldn't capture any PL37 because that railcars was good armed and use for covering of army retreat in 1941. So the most of them was totally destroyed by german aircraft and artilery because they didn't give up.
May be you can find capterud pl37 in some special books about railway but i couldn't.