AT&T has limited the access of the iPhone's FaceTime functionality to Mobile Share plan customers and LTE device users. So when the carrier announced that it would soon allow first-party video chat apps to operate on its wide network, AT&T customers were excited.
Now it seems that AT&T has started deploying the feature to a few parts in the U.S. Although AT&T has not confirmed the roll-out, a few customers from Maryland, New York, Georgia, Louisiana, California, and Hawaii are reporting activations of FaceTime via cellular.
Source: Apple Insider