so i'm going to suggest that in cities, alot of traffic and transit systems are just gsm boxes that send/receive commands. I've seen a traffic box opened up and asked the engineer how it all worked. He pointed to the (essentially) cell phone type device that sent stuff back to HQ.

I don't imagine that'd be hard to hack.

Even easier (given his hacking of a remote control) is if these points were controlled by RF signals sent by the train as they approached. "hey, it's me, open up so i can pass" type signals. This would be more shocking because it implies a level of automation that i'm not sure many would be comfortable with in such a system.