How do the Verizon world phones work? Do they have a regular CDMA device with an empty SIM slot in the back along with GSM innards to work in Europe?

I have a Palm Pre for the U.S. and a cheap unlocked oldschool Nokia that I bought on the street for something like 15 pounds in Europe. (It literally looks like a basic 1990's phone, even though it was new in its box when I bought it two years ago.) I just throw a local SIM in it wherever I go...

The AT&T GSM phones that I've seen advertised in the U.S. with worldwide capabilities have absolutely brutal per-minute rates when you leave the U.S. I wonder if T-Mobile is better since it was a European company to begin with and has its own network in multiple countries.