T-Mobile, the top opponent to the FCC’s increasingly likely plan for auctioning AWS-3 spectrum, said it still has a few plays to use as it hopes for a late-game comeback.

The nation’s fourth-largest wireless operator, with support from AT&T, the CTIA and numerous others, maintains that significant signal interference would occur against existing AWS-1 networks if startup M2Z Networks wins the planned auction. M2Z intends to offer nationwide mobile WiMAX service free of charge.

FCC officials last week said any such interference can be overcome by existing technology and that a vote to authorize the auction can proceed in the near future.

“We’re disappointed with those results obviously. The commission takes all this time and effort and lo and behold, they come up with the exact same results they came up with in May,” said T-Mobile’s Kathleen Ham, vice president of regulatory affairs. “Obviously the chairman made up his mind but there are four other commissioners.”

Ham said the companies and organizations against the auction will file a joint letter very soon, similar to a Sept. 10 letter objecting to the recent findings. If the FCC still votes in favor of the auction, then the objecting parties will consider litigation, she said. There is also the possibility of issue reconsideration by different FCC leadership under the next U.S. president, she noted.

M2Z’s claim that T-Mobile and the other incumbents are simply trying to prevent a free service offering is false, Ham added – T-Mobile is too busy competing against bigger companies like AT&T, Verizon Wireless and Sprint Nextel, plus dozens of smaller companies – and needs the clean AWS-1 network for its own 3G investment, not to keep out other companies, she said. M2Z probably chose to seek the AWS-3 spectrum instead of the recently available 700 MHz spectrum because the AWS could be obtained for a lower cost, she asserted.

T-Mobile also continues to suggest that any AWS-3 auction winner should use a technique called asymmetrical pairing, which advocates say would avoid interference and more efficiently use all available spectrum. M2Z has not commented on that suggestion.