On the Apple 4S video, about 2:25 in, they say all are world phones and both GSM & CDMA can roam GSM worldwide. On the Apple website, it says this:
Cellular and Wireless
World phone
UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz);
GSM/EDGE (850, 900, 1800, 1900 MHz)
CDMA EV-DO Rev. A (800, 1900...