The alternate list is the same as a waiting list. I was accepted off of it in May two years ago, so there was at least some movement on it, but I don't have a good sense of how much (and it probably varies year-to-year anyway).
FYI, questions like this are good to address to the admission office. Our office is good about taking calls and explaining the process to you (obviously, don't call every day, but if you have a question, by all means, ask!).
Good luck--hopefully we'll be seeing you next year!