First, no one talks on the phone at a normal volume when they're on the phone. They always speak louder in order to speak "over" the noise of the bus.

Second, yes, it totally does. The guy loudly talking into his phone is audible to everyone on the bus, thanks to the fact that he's speaking loudly. It's really obnoxious. e.g. http://www.youtube.com/watch?v=O0uTi2qkgf0

With that said, you could probably practice this stuff on the bus without being obnoxious by simply speaking more quietly. You'll still be more annoying than the quiet guy reading a book, but probably not unreasonably so.