Update: Erik sez, "Consensus on GT is this is almost certainly fake. The two GTers with access to Mazads were unable to reproduce. Faking in on video is trival -- have someone hit a remote unlock button. We're not condemning it outright yet -- the weather's too fucking cold to give a a full try right now -- 17F/-8C in St. Louis, 2F/-17C in Detroitm,-2F/-19C in Chicago, and we must note that squeezing a tennis ball that's dropped to 5F isn't trivial, and a large number of GTer work for the auto industry in some form. This is unlike the Kryptonite ball-point pen hack, which all of us were able to reproduce within a day."
Update 2: Clint sez, "Just a note that the tennis ball trick does work on some cars, but they must have a vacuum door lock system. You can also break into these cars with a toilet plunger, which must look decidedly odd."