Thank you, Gap! I think I also found the specific answer to this question for myself, a second ago. It's talking about accommodating a wc, but would be the same for a service dog. If you're interested, please go here:
http://www.rollingwiththemagicblog.com/accessible-attractions-the-haunted-mansion/
Hopefully the link works!
Beth
Beth: Thanks for the link! I went there and found out all sorts of interesting facts. A good place to go for w/c users.