For those we were unaware, there are a couple of big reasons why it's so tough to bring unlocked devices to Verizon's network. The main problem is the fact that their network is CDMA instead of GSM. This is a major hurdle for many devices, and is impossible if the device you want to bring over doesn't have the proper radios. That's not all though. Verizon has been notoriously difficult with very strict policies as well.
Luckily that is changing. If you happen to have a device that uses compatible radios and want to bring it over to Verizon, you might just be in luck soon. Because of the new voluntary code of conduct implemented by the US Government, it's now easier to get the unlocked iPhone 6 or an unlocked Nexus 6 activated on Verizon's network.
You just need to find your device's ID and pick up a Verizon SIM to make it work. We must give credit to Big Red on this one, even though they were being pressured by the new regulations put in place, this new policy is voluntary. Plus, when you think about it, it just makes good business sense. If you potentially lose a customer because they can't bring their favorite device to your network, then how is that going to help your bottom line?
As more devices are designed with greater compatibility in the future, we may see this get even easier. There may be other devices which will work as well.
Source: this phone/accessory at Verizon Wireless