Jim Cicconi, AT&T Wireless’ Senior Executive Vice President-External and Legislative Affairs, has posted the following via AT&T’s Public Policy Blog:

As most observers are aware, Apple’s FaceTime application is currently enabled on AT&T’s popular Mobile Share plan as well as on Wi-Fi, though not at this time on our other billing plans. This approach has raised questions and some concerns. We decided to take this cautious approach for important reasons. AT&T has by far more iPhones on our network than any other carrier. We’re proud of this fact and the confidence our customers have in us. But it also means that when Apple rolls out new services or changes, as it did in iOS 6, it can have a much greater, and more immediate, impact on AT&T’s network than is the case with carriers who have far fewer iPhone users.

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. 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.

In the meantime, we are announcing today that we will support FaceTime, not only on our Mobile Share plans, but also on all of our tiered data plans with an LTE device. We expect to roll out this functionality over the next 8-10 weeks. In addition, we are informing our deaf and hard of hearing customers that, as of October 26, we began rolling out several new billing plans designed to allow them to make use of FaceTime. This is part of our ongoing commitment to our customers with disabilities, and it’s a commitment which is very important to us.

We will continue to gather and assess the network data on this issue over the next few months and anticipate that we will be able to expand the availability of FaceTime to our customers on other billing plans in the near future.

Related articles:
AT&T to be hit with ‘Net Neutrality’ complaint over FaceTime blocking – September 18, 2012
Verizon: No extra charge for iPhone’s FaceTime over Cellular on any data plan – September 13, 2012
AT&T Mobility blasts ‘knee-jerk reaction’ to FaceTime Over Cellular plans – August 22, 2012
‘Net neutrality’ watchdogs howl over AT&T’s FaceTime over Cellular policy – August 22, 2012
FaceTime over cellular from AT&T available at no additional cost, but only to Mobile Share subscribers – August 20, 2012
Sprint won’t charge extra for FaceTime over cellular – July 18, 2012