Yes, for Verizon phones in the US, neither the month-to-month contract (unsubsidized) phones (when they become available) nor the subsidized phones are in any way carrier-locked.
I tested this by establishing AT&T service on my subsidized iPhone 5 before I did anything with the Verizon side of things and it has worked with both data and cellular provisioning on the nano-SIM from AT&T.
The Apple LTE page will guide you to know which frequencies are available for which model of iPhone 5. The model of each phone is conveniently printed on the back plate of each device.
The carrier you intend to get service from is in the best position to guide you in picking a US model to import, but Apple's documentation show no difference in the GSM 3G capabilities of any of the three phones available at launch, namely the A1428 (GSM), A1429 (CDMA or GSM).
I think I found the Answer I was looking for in How U.S. Carriers Fool You Into Thinking Your iPhone 4S Is Unlocked
Short answer "You can't do it!" If your phone is CDMA, its permanently locked to its CDMA network of origin.
Unlocking your Iphone 4S
Among the three major carriers operating in the U.S., only one, AT&T, will not unlock any iPhone. Because I purchased a Verizon-designated handset, the following information relates to those customers that purchase Verizon iPhones, but the technology and result is the same for any carrier.
When I called Verizon tech support to unlock my phone prior to leaving the U.S., I was told that I had to have a foreign SIM card installed in order to complete the process and that the phone would have to log in to the Verizon network on WiFi. The reason for this procedure is that the phone must validate the foreign SIM.
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So I stopped in at an Apple store in London. We logged into a WiFi network, installed a micro-SIM card from a carrier in England, and within about thirty seconds, the phone was unlocked because Verizon had already unlocked the phone at their end before I left the U.S. For the rest of my travels overseas, it worked flawlessly and provided essentially the same options that are available on any other dual-mode or GSM-only device.
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Four different iPhone 4S versions
When I returned to the U.S., I wanted to confirm that my Verizon iPhone could be ported to another carrier, whether CDMA or GSM. This was the intent of Apple when they designed the 4S: every phone is the same and will work on virtually any carrier in the world.
So, I contacted a regional GSM carrier in the Midwest that has roaming agreements with AT&T and T-Mobile. The carrier was kind enough to provide a micro-SIM card for testing in my iPhone. What I found may infuriate customers who have purchased expensive iPhones from one of the three carriers in the U.S. but at some point decide to switch to another provider because of poor coverage, customer service, or pricing.
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Sitting in South Dakota, I replaced my Verizon SIM with the Longlines Wireless chip. The phone indicated that the SIM was not recognized by the phone and required its removal and device reboot. I contacted Verizon global support to confirm my suspicions. They advised that indeed their phones were locked as against any other carrier in the United States, and that the term “unlock” only applied to overseas carriers.
I next inserted my UK SIM card into the phone, and it logged into AT&T without issue, which confirmed what Verizon told me. I then interviewed managers at three different Apple corporate stores to confirm issues with regard to unlocking.
What consumers need to understand is that there are actually four different versions of the iPhone 4S: Verizon, Sprint, AT&T, and Apple. Only the Apple phone, available from their stores or on-line, is fully unlocked and can be used on any carrier outside the United States. The other phones are permanently locked and cannot ever be used on another carrier in the U.S. Even if you spend $800 for an unlocked phone as I did and dedicate it to a single U.S. carrier, you are locked into that carrier forever if you want to keep using the iPhone. Neither Apple or the other carriers will fully unlock your carrier phone.
Best Answer
Make sure your iPhone is unlocked from Verizon. Make sure that they remove your IMEI number from the account. Verizon can unlock the device, but if you haven't paid it off they wont.