It can hapen, the mechanic who services my wifes Porsche won't touch anything near the SRS systems unless the battery has been disconnected for an hour, just in case.
My mate who fits car stereo'sset off the air bag in a commodore a couple of weeks ago. As it turns out the main cable for the Drivers Air Bag in the particular model he was working on runs parallel with the speaker wire for the drivers door, is the same size and colour too!
They even checked with Holden who confirmed that in that model some of the cars didn't come out with the regulation yellow double insulatedcoating.
The bag only got his shoulder so he was ok, but it could have been really bad.
Brett