To be honest, there is alot of ambiguity behind all this.
I'm a Doctor Who fan and this doesn't entirely surprise me. The rules have already been bent or broken and the capability to do so has been there a long time. It is within the power of, say, the Timelords to recreate and re-install regenerations in a fellow Gallifreyan. Case in point: The Master. He's used his regenerations, he's a body stealer, and he's been made extremely dead on several occasions. Come the Time War, he's back again, regenerations and all.
It has been implied for a long time that the Doctor is somehow special, that he has something different about him that allows the man to rise up to the heights of Rassilon in ways. Rassilon who, being completely immortal BTW, was pulled out of his 'tomb' for the Time War as well to be Lord President again. We know that the Timelords can restore themselves even beyond #12 with enough power and that it was even necessary in the war.
The Doctor is...last of an authority that lived too long for its own good and saw too much power in its time. But then, what are we saying? That the last of the Timelords can't keep on fighting the good fight? He always fought the Master's means of extending his life because it was wrong, or even many other people's because it was hideous. But for himself? There is a right way to do it. The power has always been there in his race. As the last, he has that entitlement, should he deem it necessary.