The folks over at iFixyouri and 9to5mac have taken a look at the internals of the Verizon iPhone and found out the device is running a dual-mode GSM-CDMA-capable Qualcomm Gobi chip. This Qualcomm's chip enables worldphone capabilities with GSM and CDMA support on all carriers, but of course the Verizon iPhone won't be able to accomplish this due to the lack of a SIM slot.
The Qualcomm Gobi MDM6600 modem supports GSM, GPRS, EDGE, CDMA, HSDPA, HSPA (up to 14.4 Mbps) and EV-DO (up to 14.7 Mbps), as well as GPS.
Rumors about integrated dual-mode Qualcomm chipsets in the next-generation iPhones and iPads have been floating around for a while now; at this point, it seems very likely that, at least the iPhone 5, will support multiple networks in a single device capable of switching from GSM to CDMA.
Update: iFixit speculates it might have been easier to support CDMA-only in this phone as GSM would require compatibility for five additional bands, while CDMA uses two frequency bands. iFixit also notes the battery on the Verizon iPhone has a new model number and the vibrating motor has a new location.