As yet Microsoft have not revealed any details on which carriers the handsets will be available with, but now it would appear that they may be exclusive to AT&T.
The news comes in a tweet from T-Mobile who replied to a customer who asked when the devices would land on T-Mobile.
@Shroedeger The new Lumia devices will be exclusively sold by AT&T. *JessicaB
— T-Mobile (@TMobile) October 7, 2015
As yet there are no official details from Microsoft and AT&T that the handsets will be exclusive to AT&T, as soon as we get some more details, we will let you guys know.