Historically they've only issued 5 non-res bull tags, but I think they increased that last year because they're so far over populations objectives. The Jackson G&F guys should be able to tell you how many bull tags they issued to non-residents last year.

Have fun if you go. They're awesome animals.

Here's a link to my 2005 hunt:
http://www.huntthewest.com/updates/updates-2005bison.htm