The Dish satellites can operate in a number of configurations and include the ability to operate at all 32 DBS transponders (really 16 frequencies/transponders; the other 16 are broadcasting out of phase = 32 transponders). Spot beaming would be a different concern, but having the remaining transponders at 119 would be tremendous addition of bandwidth, while the two(?) remaining transponders at 110 would still be a gain.
I think likely Dish and AT&T are talking in great secrecy. AT&T will have absolutely NO USE for 119 and 110, and since AT&T is ditching satellite in the long run, nor can AT&T warehouse those transponders and since there is NO OTHER BUYER, AT&T would feel it is not selling anything of value to AT&T, but of value to Dish, and AT&T wants/needs the cash to deal with its crushing debt that has started to make Wall Street feel uneasy. Of course, AT&T wants the most it can get for 119 and 110, and Charlie wants a price that is right for Dish, so an extension for a measly year at 129 when that sat has some years of life still, albeit the last quarter of its life, still enough years for Dish to extend the agreement to end of life---IF Dish did not have another option to migrate from 129 to 110 and 119 that it does not talk about publicly.