Can iphones with Verizon be switched to other carriers?

I understand the questions related to carrier qualifications and locked phones, thanks. But, I'd really like to understand the specs and the hardware before I get on the line with a first-tier support person. What I'm really getting at relates to the modem hardware in a Verizon iphone. As I understand it, Verizon iphones are CDMA-based, and are not compatible with GPRS-based networks, i.e., precluding the switch to other carriers which might only have GPRS networking.