^^ Decades late to the party!
When the EBR ban came out in NJ "way back when" there was a rash of different schemes set up to store collections in PA for NJ residents. I hauled my entire collection west across the river, bought a safe, and paid a gunsmith in PA rent for the floor-space for the safe and life was good. There was no reason for using a FFL/Smith other than that he was a friend and had an alarm system. Some other friends of mine got together as a group, rented a mini-storage spot (inside one, heated, alarmed, only accessable when it was attended, etc) and put a dozen individual safes in the spot, one for each owner. There would be no reason at all not to put a safe in Grannies cellar. In fact, there is no reason a NJ resident could not set up a PA NFA Trust and keep a collection of NFA weapons in a safe in PA. No reason not to change out "NJ" for "CA" and "PA" for "AZ, NV, OR, etc" for CA guys who want to own and shoot cool stuff.
It is SO nice to live in Wisconsin now...
Turn the lights off when you leave.