sorry to bring up an old post Lol.. but my take is that Paulie was never underboss to begin with. Tony's crew wasn't part of the 5 families in NY. He had a very small family with estimated of 50-60 made men. Tony didn't need an underboss at the time because of how small of a crew they were and also that might have just caused a problem for him. He probably just made all the capos earn for a period of time so he can decide who his underboss would be. and according to Phil, Tony's crew didn't follow all of the "rituals" of La Cosa Nostra.

and also, a street boss is the same thing as an acting boss. usually if the big guys is locked and has the street boss carry out his work.