It sounds like you need to get this horse into a smaller pen, and if he won't be caught with treats, then if he wants to run away, make him work...turn "his idea" into YOUR idea... Horse are lazy by nature, and he WILL figure it out that allowing himself to be caught is way easier than the alternative (work). You don't necessarily have to make him canter, but make sure he's not just loafing about either, and change directions often, so he realizes that you are the one calling the shots.
That said, if the owner can't work him, then maybe she needs to send him to a trainer, or sell him...he's the way he is because he's gotten away with it, for a long long time, and ONLY persistance and consistency is going to make him change his current behavior.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."