I'd be interested to see stats on fuel burn for this. OK, if you're going to end up in a queue for a while, I'm sure that you'll save fuel with an engine shut down.
However, if it takes (say) 3000lbs thrust to move the aircraft, you either need 2 engines producing 1500lbs each or 1 engine producing 3000lbs (prob a bit more due to the asymmetry).
I wonder what the difference in fuel burn really is (assuming no queueing)