Contradiction in prevention of cell-phone controlled bombs?

By now, on the heels of the bombings in London, you've probably picked up on the debate regarding the use of cell phones in tunnels.   Immediately after the bombings, cellular phone service was discontinued in the four major tunnels leading into New York City's burrough of Manhattan.  Although New York City officials did not comment on the move at the time, the move appeared to be driven by the possibility of remote detonation by cellular telephone (cellular service resumed in two of those  tunnels today).  It just struck me as sort of odd that, at the same time we're trying to eliminate the possibility of remote detonations in certain highly vulnerable situations (tunnels), we appear to be improving that possibility in others (passenger jets).