Thanks for posting this info, Matt! I didn't know it was banned during sporting and music events. I'd imagine that would help considerably with it being a problem. How is enforcement of rude or obnoxious behavior?
As a former regular Caltrain commuter, I did not find alcohol a widespread issue. There are times where it is problematic, but it is irregular and I do not believe banning alcohol on Caltrain is a good idea.