Since you are talking about EAS and I don't want to bring this up at this point in the Oklahoma thread (where I live):
Do secondary EAS stations receive their notification of an EAS activation by monitoring the broadcast signal of a primary?
The reason I ask is: Yesterday here in Oklahoma City, I was listening to the simulcast of KWTV channel 9 severe weather coverage on KOKC 1520. At at least two points when I really needed to be listening to the vital, real time ground truth reports from KWTV's spotters and meteorologists, the simulcast audio was interrupted by an EAS broadcast for storms in southern Oklahoma. If there is some back channel way of triggering downstream EAS stations and there is an option to opt out of broadcasting messages, I would much rather not have had the live coverage interrupted.