I was accepted into MSUCOM's Class of 2007, but am defering for one year in order to establish residency. I had to send in my deposit like everyone else, but had to write a cover letter asking for permission and my rational and reasons. As far as I know, it was pretty automatic for residency purposes. I did talk to someone at my interview who was a resident of Michigan and had been accepted last year but was denied deferment. I think they didn't approve of his reasons--he wanted to travel across Europe. So he had to reapply. I think as long as you have a good reason.
It probably is a school by school basis. You probably would have to contact the school directly to know what procedures there are and their specific criteria for this.
-=Eric