Southwest has pissed a couple of controllers off and paid the price for it. Last year a Southwest flight was taxiing toward the gate in Orange County when I called for a push and was cleared to do so. The ground controller then told the Southwest flight they would have to wait until we were clear to get to the gate. Hearing the exchange and realizing we would be pushing back directly behind their gate and blocking them, I offered the controller the hold our position until they parked. He told me that was not necessary and to "start the push back now"...and we blocked the Southwest that was about 3 gates away from their parking spot.
Also, one of my friends heard them pushing back and blocking the taxiway after they had been told to hold position at the gate in an attempted to beat the pack out from the morning curfew. When the ground controller realized it, he told them they hadn't been cleared and asked what they were doing. The SW crew laughed into the radio and said there had been a misunderstanding with the ground crew. The ground controller told them to pull back forward into the gate. SW said they had already disconnected. Ground said he could still see the tug in front of the plane and to have the groundcrew reconnect and pull them forward as they wouldn't be cleared to taxi until all of the other traffic had taxied out.
I would love to have seen the expressions on the flight crew. Usually when they pull that crap, they get away with it.