With most wait lists if you haven't been called by the time the 2nd or 3rd day of class rolls around, you can assume you never will be. I don't think there's a notification system if you're NOT being pulled off. You just sit and wait. It sucketh.
I will say that what I've heard from people in admissions is that the closer it gets to the time school starts, particularly as it gets later and later in the summer, when they start having to go to the waitlist they are looking for people they know will say yes. So that if you've continued to keep in touch with them, and have told them repeatedly that you will up and move from wherever you are just for a chance to be at their school, they are more likely to call you instead of someone else. I've also heard them say it helps if you have family in the area or are from the area because you have a place to stay if it's really down to the wire.