I *think* almost all of the backstage tours are accessible now, but even just a few years ago, there were still a couple of them that were not accessible!
Be sure when you book any tour or special event at WDW that you let them know if you have accessibility issues.
@loriwvu I found the page for the
Keys to the Kingdom Tour, and if you click on the "Accessibility and other Information" link on the right, you will see that it states that for this tour "May Remain in Wheelchair/
ECV"