Verizon iPhone 5 is shockingly not only unlocked right out of the box but also supports GSM, which essentially means that you could use it with AT&T and T-Mobile, if you chose to do so.
Verizon iPhone 5 runs on AT&T and T-Mobile too
iDownloadBlog confirmed that the iPhone 5 with the US Verizon carrier is a GSM unlocked handset too and owners of the handset could file down any micro SIM card, regardless of the fact of it being for AT&T or T-Mobile and use it in the device.
The Verizon version of the iPhone 5 could get the HSPA+ service of AT&T, along with their 4G and it also works with the network of T-Mobile too. You do have to bear in mind that if you wanted to use it in this way, you would have to be in the right service area, if you wanted to use the other networks.
But given that it is unlocked, the it may actually be cheaper to buy a Verizon iPhone 5 and pay the early cancellation fee as compared to getting it directly from Apple for one of the other carriers.