How about sending notifications in the other direction? (Makes more sense)
It makes a lot more sense to me that any emergency declaration/notification be sent to the public via text message, Twatter, & Farcebook than to use the "Emergency Broadcast System" on TV or Radio (A cold war throwback from the "duck and cover" days of my youth)
Unfortunately, this generation will continue to text away as the tsunami rolls them into human mush.
The fact still remains that TV and Radio over the air broadcasts are more likely to be operating in an big emergency than any overall phone or IT communication backbone.
Most TV & Radio broadcast transmitters are located at the antenna (usually out in the boonies) and have generator power available.
A few hundred watts will go a LONG way on radio. I assume the same for TV.
Cable, Internet or telephone relies on various fiber/copper backbones so there are a lot of potential points of failure.