As far as I'm aware, the 3G comment is uncorroborated. The anti theft system only works if the user has installed a 3G card. The chip can then access this card, decrypt the kill SMS and shutdown the chip.

Also think about it - you're locking the processor onto a board which mostly made of metal, under a big block of metal to cool it and then you're surrounding it all in a metal box with more metal around it. A 3G signal is no match for a Faraday cage.