Facing criticism — and consumer complaints to the FCC — over its decision to limit the non-WiFi use of Apple’s FaceTime video chat app to customers who have shared data plans, AT&T announced yesterday that it will allow folks with the iPhone 5 (but without unlimited data plans) to use the app over its network.

This means that AT&T customesr who have the app installed on a non-LTE iPhone or who still have unlimited data plans are still only able to use FaceTime over a WiFi connection.

In a post explaining the move on AT&T’s Public Policy blog, the Death Star’s Jim Cicconi writes that because AT&T has so many iPhones on its network, the introduction of a new app that goes out to all iPhone customers in a short time can sometimes have unexpected consequences.

“In this instance, with the FaceTime app already preloaded on tens of millions of AT&T customers’ iPhones, there was no way for our engineers to effectively model usage, and thus to assess network impact,” explains Cicconi. “It is for this reason that we took a more cautious approach toward the app. To do otherwise might have risked an adverse impact on the services our customers expect – voice quality in particular – if usage of FaceTime exceeded expectations. And this is important for all our customers regardless of which smartphone they may use.”

AT&T says the FaceTime over cellular functionality will roll out to customers over the next 8-10 weeks. (UPDATE: A rep for AT&T tells Consumerist that the FaceTime over cellular will also be made available to customers with LTE-enabled iPads.)

However, AT&T’s decision is not dissuading advocates who say the company’s FaceTime policy violates the FCC’s Open Internet rules, which state that “mobile broadband providers may not block lawful websites, or applications that compete with their voice or video telephony services.”

“The law is clear,” said Free Press Policy Director Matt Wood. “AT&T cannot block FaceTime based on claims of potential congestion. There’s nothing even remotely reasonable about that approach. AT&T simply can’t justify blocking an app that competes with its voice and texting services unless customers purchase a more expensive monthly plan that includes an unlimited amount of those very same services. AT&T’s course correction is a move in the right direction, but until the company makes FaceTime available to all of its customers it is still in violation of the FCC’s rules and the broader principles of Net Neutrality .

As I’ve argued in the past, I don’t believe that AT&T’s policy necessarily violates the too-vague Open Internet rules. I do however fear that only allowing certain classes of customer to have full access to an app opens the door to a scary new world in which wireless carriers have even more say over which apps you can and cannot use on your phone, and what you’ll have to pay for unfettered access.

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