If I'm stood next to a friend, at the bar or at the urinal, I'll chat away just fine. I don't try to start conversations with strangers at urinals but then I don't try to engage strangers in conversations anywhere.
Unless you have a specific reason to talk to someone (asking for help, the time, directions, etc.) then I very rarely see any strangers interact in non-social public environments. If I start talking to some random guy on the bus or in a queue at a supermarket, he'll think I'm a bit weird. It's not really got anything to do with bathrooms except, maybe, that no guy thinks of a toilet as a social environment (except maybe the cottagers...hehe)