They wouldn't have to be cleaned up to be put at that resolution. The resolution of 35mm film is greater than 1080. Most likely what would happen is it would be scanned at around 2000 lines of resolution and then scaled down for HD.
And if we're going to get really technical, AOTC and ROTS weren't filmed, because it was a filmless process. They were either "shot" or "taped".
I don't mean to come off like a know-it-all prick, I'm just a finicky film student.