It is part of the response plan to shut down all cellphone service. Many of the terrorists use cell phones to remotely detonate the bombs - they wire a cellphone to the detonator cicuit so when the cellphone rings the bomb explodes. If you disable all cellphone service, the terrorists are not able to dial-up the cellphone and have it trigger the detonator.
The US has this cell phone shutdown feature in effect as well - as soon as an authorized LEO or government agency determines there is a legitimate bomb threat they can directly disable cell phone towers in the affected area(s) - even without contacting the cell phone carriers. They have this feature implemented in almost all major metro cellphone areas.
They also use wide-spectrum RF jammers to block certain mobile radio frequencies. Both mobile jammers and fixed jammers (mostly prepositioned in high-density urban areas (NYC, DC) and high-threat areas (airports)).
How would this work with that satellite phone service?