I doubt if they even scraped the paint off either wing.
The sad part is - I heard passengers on both planes were stuck and could not return to the gate for several hours while officials from both airlines pointed fingers at each other and waited for the FAA.
Keep Austin Away
The United captain wouldn't have been able to see his wingtip from the cockpit, so ordinarily they would rely on taxi lane centerlines to provide sufficient clearance. In this case, though, since the pushback distance could vary, it probably relied more upon a judgment call by the United captain, and he clearly made the wrong choice.
So, probably several factors involved. Regardless, if all they did was ding up the winglets, that's a minor issue (though a major inconvenience while they investigate).
Bad touch! Bad touch!!