Google said that T-Mobile band 12 LTE support would be available for the Nexus 5X and 6P by the time they ship, but unfortunately, that hasn’t happened. Thankfully, one of the devices may be very close to getting the promised support.
The Nexus 6P has appeared on T-Mobile’s list of devices that support band 12 LTE, also called Extended Range LTE by T-Mobile. Though the device hasn’t received an update to add this support, the fact that it’s on the list bodes well for the update coming in the near future. Unfortunately, there’s no sign of support for the Nexus 5X yet.
For those with a Nexus 6P on T-Mobile, keep an eye out for an update to enable band 12 LTE support