It sounds like off-contract iPhones aren't the only ones AT&T has begun to officially unlock -- they're also quietly offering unlocks to on-contract members of the US Armed Forces on active deployment. MacRumors says they've confirmed what's taking place.
Carriers are required by federal law to suspend service without penalty for deployed military personnel upon presentation of their military orders, but AT&T is not required to unlock the phones of deployed service members. Instead, the company is choosing to do that on its own.
AT&T wouldn't comment on the story. If you're a member of the US Army, Navy, Air Force, or Marines and you're on deployment, and want your iPhone unlocked, give AT&T Customer Service a call.