I think the correct response to your question is that it doesn't matter. Every year they do things differently. Obviously, this year they are behind in the process if they haven't submitted summer WL status emails/calls to those on the summer WL, as they stated would happen last week.
Bottom line - if you get accepted, you'll most likely hear when someone decides they want to go to another school. It appears the class is full, so you won't hear anything until after June 6th, which is the payment deadline. If someone drops, you will probably hear something fairly close to that date.
I'm guessing around June 6th, they'll start dinging more people and leave a handful on the summer WL.