Default [Q] BYOD Galaxy Nexus on Metro PCS USA

I tried looking around earlier but I couldn't really find a definite answer. With Metro's bring your own device plan
it says the galaxy nexus is compatible to be flashed to metro, is this correct?
Are all galaxy nexus's unlocked or do I have to buy a specific model, like the verizon or sprint model?
It doesn't really specify on their website.
Any help would be appreciated.