Greg:
I was Director of Photography for the US Air Force in Europe from 1976 to 1980 and saw a lot of West German railroad activity. I would have been shot if I tried to do the stuff in East Germany. I attended a joint USAF/Soviet Air Force meeting in Postsdam in 1979, but we were not allowed to take any cameras with us (they took me along because I had three semesters of Russian history in college). You are right about being able to go back in time on German rails. Closest to that in the US is the EBT in my opinion.