No. Because only one device is getting ATT's data. The speakers are not getting data - their getting bluetooth data from the iPhone.
Why is this so hard for some people to understand. And why do people think I am saying ATT's policy is the right one? I'm just stating how ATT views their one device/data plan policy.
AirPlay works on Wifi. So again - ATT is not providing data to another device. Your iPhone is taking ATT's data and then uploading it via your own wifi signal.
Nope, it is you who is not understanding that data is data. The phone transmits DATA to Apple TV, which then transmits DATA to the AVR through the HDMI connection. These are clearly DATA TRANSFERS and are no different than tethering.
Similarly, the voice (or music) DATA from the phone is transmitted through BT to the car audio system.
You are simply conditioned to think that because AT&T has put something in their boilerplate contract and interpret it a certain way, makes it valid.
It's a scam and they know it, but it makes the phone companies money and until the FCC starts doing its job, the consumers will pay.
BTW, I do have tethering built in into my Galaxy Nexus (running Android 4.1) and I do tether at airports and such. I've done this for years now (on T-Mobile).