I just learned about this fascinating little piece of Chicago television history.
This is one of those things that's amazing and creepy at the same time. Amazing that he was able to pull it off twice (the second time, uninterrupted by the station) and that he's never been caught. As for the creepy, well, just watch for yourself.
My hat's off to you, though, Max Headroom dude, wherever you are. Very cool trick, even if it was illegal.