CDMA phones (Verizon, Sprint PCS, Alltel, and U.S. Cellular) won't cause any interferance due to their network setup. (CDMA is based on spread spectrum, and looks like background noise)
GSM Phones (AT&T, T-Mobile) can depending on what frequency set that the carrier is using at that location. (is based on packet info, and will cause bursts to occour)
Still though, i'd rather someone not talk or text, until the taxi back to the gate.