I know - it is a problem. But, the only option available is to disrupt their plans. Now, they don't have the satisfaction of knowing that their cell phone activated plans will work. And, we can turn the signal back on when we wish.
I would expect we will see continual disruption moves by our Homeland Security. Why give the enemy free reign over our systems. Make it as hard as possible on them and keep throwing them off their game.
Perhaps we already have?