for the more mundane use like tornado warning...
Not a direct reply to you, Les, but your comment reminded me of something.
The Emergency Alert System is supposed to provide information about disasters and other major events, but except for weather alerts, I can't recall ever hearing any stories of people getting useful info through the EAS system. I mean, it would great if your SAME-encoded weather radio, which is always "listening", would perk up and say, "Hey, here's an important message from the mayor regarding incident X! Listen up!"
I know that I haven't heard anything myself over the years, even when I was in Manhattan on 9/11 or through earthquakes in California. Actually, maybe the more major and chaotic a situation is, the less likely officials will be broadcasting official EAS messages.
In any case, seems like most useful info flows through news bureaus and are disseminated through commercial sources, hence the usefulness of a battery powered AM/FM radio.
Scanners can be useful but as many agencies go to more sophisticated digital systems, and even encrypted systems, scanners seem less useful in many areas without spending a lot of money.