It's also a good move because it shows that Apple isn't set on completely cutting them out of the picture. They could have easily gone the "All FaceTime audio/video" route which cuts the carries out of the equation, except from a data perspective, which is probably the most taxing aspect on a network.
But, what does this mean for Apple? Maybe the carriers will be more willing to play ball with Apple because they are not trying to completely exclude them from the equation?