The actor who played NON has been answering questions at IMDB's message board for almost a year. Sounds like he's not a big fan of Richard Lester.

He says that Donner shot a scene where the villains are taken away by the cops at the end of Superman II... I think you can actually see this happening in the background of one of the deleted scenes in the DVD, the one where they're taking Luthor away. He also claims that Donner had plans to bring them back in future movies.