I have the same problem - it has come up just today for me.
Ever since the option of using phone number for iPad (running iOS 6) and Mac (currently running the latest version of Mountain Lion OS) has been offered, and after I have accepted it, I've been able to receive FaceTime calls placed to my phone number on all three devices.
However, earlier today it stopped working. FaceTime on my Mac and iPad went back to using just the e-mail addresses associated with my account for FaceTime calling and FaceTime calls placed to my phone no. are no longer coming through to Mac and iPad.
Anyone knows how to resolve the issue?