Audiovox CDM-9900

If there was anyone who lives or lived in NYC during the attack of the WTC knows how important cell phones were. Verizon Wireless was, I believe, the only cell phone provider offering cell service at the time of the attack. Which was very crucial in those grueling moments. Now analog mode played a very big role that day. Not once did a call get dropped during analog mode. Now my question is...if god forbid...something like that happens again would digital phones work even with all this new technology or is analog still the back up mode???