The Incentive Auction has concluded, however the results are still being tallied and the FCC has not yet stated who spent what, who got what and so forth in the auction. But analysts have done some calculations and believe that AT&T spent around $2.4 billion on this auction. Now of course, this shouldn't come as a huge surprise, given the fact that the forward auction netted around $20 billion, which was much less than what many expected (numbers as high as $70 billion were floating around before the auction started). Analysts had also predicted before the auction that AT&T wouldn't be a big bidder in this auction. This was partially due to the FirstNet contract that the company got, which gave them more 700MHz spectrum to work with.
Additionally, AT&T noted in a filing with the SEC (Securities and Exchange Commission), that their "commitment to purchase 600MHz spectrum licenses for which we submitted bids is expected to be more than satisfied by the deposits made to the FCC in the third quarter of 2016." Although, AT&T didn't disclose how much they deposited to the FCC, which the deadline was July 1st, 2016 to do so. Analysts from BTIG seem to believe that AT&T had set aside around $2.4 billion for this auction, with T-Mobile setting aside around $2.2 billion.
The FCC is expected to announce the results of the Incentive Auction in the coming weeks, and many still expect T-Mobile to come away with a hefty amount of 600MHz spectrum. AT&T and Verizon will likely pick up a good bit, but they aren't in as desperate need for low-band spectrum as T-Mobile is, who only picked up some 700MHz spectrum from Verizon and a few other regional carriers in the past few years to help build out their LTE network. Sprint wasn't even part of the auction, as they decided that their 800MHz spectrum from the disastrous Nextel merger was more than enough, and with 5G coming in pretty soon, high-band spectrum like their 2.5GHz spectrum is going to be much more important, as it can hold a bit more capacity. Sprint is already using their 2.5GHz spectrum on their LTE Plus network.