You realize that link is from February of 2013, right? A very long time ago and also before Softbanks purchase of (80% of) Sprint, and before the completion of purchasing the remaining stake of Clearwire.
I'm not sure why everyone keeps suggesting that Sprint sell some of it's 2.5 GHz assets. It's not going to happen. 2.5 GHz is the key to Sprint's comeback as a data strong network, and they aren't going to risk their comeback by giving it to their competitors. If Sprint participates in the 600 MHz auction, it will be financed by other means, not by the sale of any of 2.5 GHz.
-Anthony