Yes, but leaving there at that spot, by running against the wall, seemed quite ridiculous. It was done once, though. There was a demonstration in (I think) the mid 80's when West Berlin demonstrators ran from the police and escaped to the centimetres next to the wall that belonged to the east and actually onto the wall. The West Berlin police never crossed that invisible border (the wall was completely on eastern territory, so to the west of it there was a strip belonging to East Berlin). It was nice pictures in TV and press, I remember, and they had to explain that this happened because of the brutality of the police. The demonstrators later left over eastern territory and then back to the west by U-Bahn. Took some negotiations with the Vopo.