Though they've been dragging their feet, I imagine that the city of El Paso will be taken care of sooner rather than later. License Acquisitions, on the other hand, has been a constant PITA throughout the rebanding process. I'm guessing that they've been hoping for some financial windfall from Sprint in exchange for their cooperation. They've been stalling for years. Whatever it is that they're looking for, they need to just go away at this point.
The network we will all be on eventually. (Core/Host network) T-Mobile's network is the host network... then when you add the equipment from Sprint, and the frequencies and band width, you end up with the New T Mobile Network.
Remember 2 years ago... the plan was to add and bulk up the T mobile network... then transition all the Sprint people to the T Mo network. Sprint's network would be taken apart and equipment and some sites would be reused. Hope that helps you understand.