I dpoke at length to the tech at a nearby Verizon that was robbed at gunpoint.
Apparently modern devices can brick themselves once they detect a cell or wifi when they broadcast their MAC address. And unless you are in the Himilayas such a signal will be found.
Even if they are older they can never be activated.
And any attempt to activate will broadcast the GPS location.
It is multilayered.
Well, when that tech turns on the phone it sends out an IMSI to see if any cellular carriers knows about the phone SIM card. If not then it is up to the tech to type in something on the phone to register the phone on their network and something on their network to allow the SIM. Can't brick itself based on that. Also the SIM can often be removed and the new IMSI won't be in the brick-yourself database.
The other choices are MAC and IMEI. But those require a network connection, then the phone would have to be programmed to look itself up in the brick-yourself database based on IMEI or MAC. The MAC is used to get an IP from a router and doesn't go beyond the router, but the phone can get the network connection and send IMEI and/or MAC to the retailer's network to find out if it is in the brick-yourself database. That'a a theoretical possibility.
That iniital lookup could be blocked preventing the phone from doing the lookup. In fact if the retailer's server is down, the lookup won't happen. The GPS location might be useful for the cops but can't be used for the brick yourself feature. There's not going to be a database of locations (e.g. stores) to not brick yourself. Also GPS can be unavailable.. No layers, just a database. Were all the IMEIs or MACs known for phones in the inventory, can they subtract the remaining phones at the store from the list, then put the list in the brick-yourself database? Maybe. But you'll need a real tech to explain how.