Opening cars with a tennis ball

Watch this video of a woman opening a locked car with a tennis ball. Brought to my attention in a Digg post.

Like a lot of people in my business, I do a little lockpicking, though I'm not particularly good at it. I'm curious if anyone knows exactly what is going on in this particular car door lock. I'm curious if the wafers and sidebar are being pressed into place by the air pressure, or if the air is actuating the lock pull linkage, or what.