One of the YC App questions involves detailing a story of a real life hack. I know he didn't fill out the app, but I certainly hope that figuring out public transportation falls above the bar.
Figuring out how to use a system as designed isn't much of a hack...it would be more of a hack if he figured out how to reconfigure the system to route a bus or train directly past the front entrance of the building he was trying to get to.