(Originally submitted last January, but unanswered.)

While reading about the Berlin U-Bahn on Wikipedia, I noticed that Friedrichstrasse station was in East Berlin during the Cold War - but a number of platforms were still open to West Berlin streets, and West Berlin commuters regularly used it.

Were there any difficulties with this unusual arrangement? Did East German police ever hassle West Berlin travelers in the station? Did anyone (such as escapees from East Germany, or well-known anti-Communists) have to avoid the station because of this?