Yes, all Pixels are carrier-unlocked. They can be used on any carrier.
The exception with ones sold by/for Verizon is that they are bootloader locked - you can't unlock their bootloaders to install custom firmware. Other than that, though, I could purchase one from Verizon today and use it on T-Mobile tomorrow. I know many users who have done just that so that they could get the "panda" or blue-ish colors which are Verizon exclusives.