For what it's worth, one of the scenarios Sammy Gravano and John Gotti considered for killing Paul Castellano was to assassinate Paul in a diner he always ate at. Paul's booth was near the men's room, so their plan was to send in someone Paul didn't know, have him walk into the men's room, and then come out shooting. Sound familiar?

Could be a coincidence, but it's obvious from the show that they took a lot of inspiration from real mob stories.