Be careful, ATT and other version have incompatible firmware/APK/sbf. I have an ATT.
Motorola had locked down this phone essentially with two security layers:
The first is the bootloader, it boots a kernel only if it is correctly signed with a certificate. Apparently there are no way to unlock it at the moment XDA unlock thread!, Kexec and 2init method are on the way.
The second is Tomoyo, we can bypass some checks editing (only with a rooted phone) /etc/tomoyo/domain_policy.conf or (re)moving /osh/sbin/tomoyo-init and /osh/sbin/tomoyo-start files.