I don't remember (or can find) ever stating that each track had to use different sources from the others. I'm not listing what sources each editor is using to keep the project secret and also because I don't mind the same source being used on multiple tracks. I have however been keeping track of sources and trying to keep the same source from being used too much.
CtS, yeah, I believe there are plenty of HD sources with which a project of this magnitude can be made using all HD sources. These sources can be gotten from multiple locations, even here in the states. I've opened this MEP up to editors from around the world. When I first began this MEP there wasn't a whole lot of HD footage available in the states, but now there is a lot more, and even more can be gotten from overseas.
Honestly, I wouldn't really care if someone were to find a 1080p RAW from a series being released currently and then downscaled the source to 720p and used it. In fact, that method would still produce a better looking video then a 480p DVD that has been upscaled.
As I state in the MEP information page, the point of this project is not so much about the anime used, but about the eye candy and motion graphics that are used. It is with this consideration as well as where the final product is set to air that I chose 720p as the final format for this project.