EAS is a neat system. From a hacker perspective it’s interesting to think of the cascading effect that some well placed broadcast signal intrusion could do.
While I think it’s a good idea to test this system from the top down, versus at the station level as done in the weekly tests, the work to get the word out about ignoring the upcoming test undermines the system. We’ve essentially created a small window at a predetermined time, in which the system will be busy relaying test messages, and to which people have been prepared to ignore. Of course, this is all a bit of a moot point since we’ve never actually used the emergency alert system for anything terrorist related before anyhow.
Several interesting things can be gleaned from the Wikipedia article on EAS incidents. Based on the September, 2010 incident, it sounds like in-band signalling is used for activation, and that the system allows for replaying of messages. Based on several of the incidents, it would seem like people don’t really pay attention to the system anyhow.