Street gangs are too busy fighting each other over their niche - the drug trade in their geographic areas. It's not like they're going to just up and decide one day to make a move on the mob's video poker machines in suburban bars or whatever. Again, different worlds where the overlap is more the exception than the rule. But this seems almost disappointing to people who apparently watch too many movies.
The times when the mob has been dominant over black street gangs is when they had to control over the drug trade. Back during the French connection and when Carmine Galante was in power I think is the most realistic way to see how how the mafia was dominant over street gangs without seeing a (non-believable) city-wide war.
