If you know these things, then explain it.

I don't know exactly what I am talking about. But NT on embedded? NT is designed for any kind of CPU, but not any kind of architecture. It requires PCI bus for instance. Without a PCI bus there is no way of doing the timing right for instance, well everything handled by the bus. NT has no mechanisms to handle any low level HW stuff that isn't supported by a standard bus. Very much unlike CE that is able to run on everything.

It's probably not impossible (WinRT obviously works), but a complete rewrite for every configuration would be needed. As I understand WP only runs on one particular architecture, and who knows what that looks like? I mean who on this board. Do you? The WP8 hardware architecture may very well be made to support NT, not the other way around. Probably a combination.

NT not being able to run on WP7 HW sounds more plausible than not to me. But what do I know? You are obviously such an expert, please explain.