I'm thinking about other reasons too. The international licensing sounds like it could happen (but then why can they do AF with Sony? Are they not also Japanese?).
How about this:
SigRonKina reverse-engineer the AF routines, rather than license them, as we all know. If ever a new camera body comes out, if Canon's changed anything, sometimes older lenses don't work. It's happened before, it'll happen again. Sometimes you can send the lens in to be re-chipped, some are just too old and you're stuck with MF or you have to use an old body. Some people steer clear of 3rd-party AF lenses specifically because of this problem.
Now imagine if Zeiss did that? They have a very good, well-respected name behind them. Maybe they can't license the original AF (from international issues, or whatever, ever notice how noone else licenses AF from Canon? Maybe Canon just don't want to license?). They probably don't want their good name being dragged down to the same level as Sigronkina from some simple AF issues, so it's better to stick with MF...