Here you would get alerts even if not registered on a network, as long as it is connected to a tower it can connect to emergency services. Very useful if you have extra phones, make sure to charge them every once in a while. If the battery loses too much voltage it won't be able to hold a charge if not charged occasionally. We are accustomed to them with hurricanes and floods. But most other people are accustomed to getting regularly buzzed with child abduction alerts\Amber Alerts. You can turn them off but most leave them on so an entire room can go off as they trickle out. It's easy enough to live with but I think also people dismiss it.
We can also get "Presidential Alerts"... no idea where that would fall with the below, though:
I've seen Extreme issued before to our local area. Very fun to get those because they come in increasing severity and so lots of buzzing while you sit around in the dark. But they are worth having rather than not because if you are out of power you really can't check anything reliably if tower data is lost or reduced, but emergency messages probably have higher priority to get pushed out when cell tower is on generator power. Keep your laptops charged also because in many cases they can be used to charge your phone even while off as long as they are in standby.
/psa