What was ever the logic of getting John B-B onto that train?

!It never made sense to me what was the hijacker's point in getting John Bailey-Brown onto the train. Of course in the end we find out why, but why did nobody question through the whole thing what was supposed to happen when JB-B got onto a train with no hostages left on it? How was he supposed to escape? It's not an aircraft or an untraceable yacht. He would just have been recaptured or gunned down by the authorities. So, why did it take until the end of e8 for Otto to figure out that it was an ambush for JB-B? That is the biggest hole in the entire premise. It might have made sense if the demand was to get him onto a plane and only release the passengers once he landed in Russia or some rogue state without extradition. But to put him on an U-bahn with no exits except to the surface streets of Berlin crawling with police? Non-sensical.!<