The news comes shortly after it was reported that AT&T unlocked an iPhone 3GS, but only after Apple CEO Tim Cook stepped in and asked for them to help. The user was moving to Canada due to a job relocation, had long since completed his contract, and wanted his iPhone 3GS unlocked.
Here's what AT&T said in the statement they sent to media:
"Beginning Sunday, April 8, we will offer qualifying customers the ability to unlock their AT&T iPhones. The only requirements are that a customer's account must be in good standing, their device cannot be associated with a current and active term commitment on an AT&T customer account, and they need to have fulfilled their contract term, upgraded under one of our upgrade policies or paid an early termination fee."
This is a huge change from AT&T's prior policy on iPhones, which basically said "sorry, no unlocking, no matter what." That left users with having to jailbreak their iPhones.
Just remember, though, if you want to unlock your iPhone so you can use it on T-Mobile, those carriers have incompatible 3G frequencies so you will be stuck on EDGE if you try to use a T-Mobile SIM.