A question about the train station (possible spoiler)

This could be a spoiler so consider not reading if you haven't seen the film. In the beginning when the West German is in West Berlin at the Train Station, he's on the phone and a man in shorts and an undershirt is staring at him. Could he have been an informant for the Stasi and something to do with who helped get him caught. Also, right before he's arrested, a man in his compartment is reading the paper and gets up and leaves just before the police come and get him. Could that have been the same guy as the one in the undershirt at the station. From studying the cold war, I learned that the East Germans were willing to employ pretty much any West German willing to do any kind of spying. It could make sense that they have guy pose as a destitute in a train station. It could have also just been a homeless man. They are everywhere in the big cities. Anyway I just thought it was strange the way they seem to focus on him right before he's caught.