Last month, AT&T said that it would allow any native video chat app to run over any LTE enabled Apple, Android or BlackBerry phone by the middle of June. Note that this did not include the operator's HSPA+ network, which nonetheless, has been supporting FaceTime based on the anecdotal evidence from AT&T customers. By the end of the year, AT&T plans on allowing any native video chat app from any device to work over any network.
When FaceTime over cellular rolled out with iOS 6, AT&T at first limited the service to those with a Mobile Share plan and LTE subscribers with a tiered plan. But by November, AT&T started dropping some of its restrictions that limited the iOS video chat to certain Apple devices.
Whatever AT&T was fearing apparently never happened. When the restrictions were first announced, it was believed that the carrier was worried about taxing its network by allowing video chat over LTE and HSPA+, but thankfully for customers of the carrier, those worries are gone.