[VLM]

I'd disagree in that:

1) No signal = the primaries have gone off and the area is swarming with panic evacuees and rescue personnel and full of news cameras = almost the definition of the perfect time for the secondaries to go off.

2) If the purpose of the attack is terror, what better way than shutting off communications then creating an intense demand for communications? And you get to make the authorities feel guilty about it?

3) This also fits in with jammer mentality. So if a jammer protects against IEDs, the obvious counter response is a weapon against jammers. So next year's run, if there is one, will have a motorcycle pace vehicle with a very highly publicized jammer mounted on it for the purpose of security theater, the pace cycle/jammer rides past the trivial to imagine and design jammer detector, and ...

It all boils down to I can't figure out a realistic alternative way for the good guys to help the bad guys more effectively than shutting down the cell network.