I'm pretty sure the original clips from Empire of Dreams are film sourced. It might not have been in that great of condition and required a lot of clean up to use. They look different from the actual Gout (Han Solo running away from the stormtroopers) Someone once pointed out that an animorphic clip from Empire at Cloud City showed a ship flying by without the 97 correction to match the orange sky and it still had the matte line. (the thread was "I think the oot WAS restored.")

Actually, I think I know of another scene that would test this: The original entrance to Mos Eisley. Near the end of EoD, a few short before/after clips are shown of the new effects. There's very obvious DVNR smearing on the THX version in this shot. Any pre THX release could not look nearly as bright with the correct color as the sample from EoD. So does the animorphic widescreen clip from the documentary have the smearing?
This is from dvd active, they have a guide to the alterations.

http://img522.imageshack.us/img522/5405/speeder1977af6.jpg

This clip is also shown on the feature about the special edition from the 97 video release in pan & scan. Anybody know the source for those original clips?