As someone who used to take the commuter bus from Santa Rosa to San Francisco every day, there are ways to stop people from being rude. And I commend Amtrack for their final decision.
The general, unofficial rule on the commuter bus was you could talk quietly between getting on and the last stop before we hit the freeway. After that, you were expected to read your book, watch your movie (with headphones), or sleep quietly. Any cell phone calls that came in during that time should be very brief, and very quiet.
Occasionally there would be a new person on the bus, and they would be the type to talk loudly the whole way home. For most people, a chorus of "Shhhhhh!" was enough to get them to comply. But I have seen people get into a loud argument over it. The bus driver would usually give them a stern look, and that would settle it. But once, to many cheers, the driver pulled over and kicked someone off the bus (at a bus stop).