NEW YORK ( TheStreet) -- AT&T ( T) and T-Mobile, in an unprecedented move, said they will open their cellular networks in the wake of Hurricane Sandy. In a joint press release, the competing carriers announced an agreement allowing subscribers access to each other's frequencies during the crisis. "Customers will be able to place calls just as they normally would, but their calls will be carried by whichever network is most operational in their area. This will be seamless for AT&T and T-Mobile customers with no change to their current rate plans or service agreements even if the phone indicates the device is attached to the other carrier's network." T-Mobile and AT&T each use similar wireless network technology based on international GSM and UMTS standards. That allows for this extraordinary sharing of voice and data traffic. Current estimates show there is damage to nearly one in every four cell-phone towers in the affected areas. In addition to cell phone repeaters and antennas, towers also help handle 911 calls, local distribution of pay and cable TV signals as well as Internet services. --Written by Gary Krakow in New York. >To submit a news tip, send an email to: email@example.com.