If you've been patiently waiting for Android 5.1.1 on your T-Mobile -activated N6, but can't flash the over-the-air update after applying some kind of software modifications, now you can grab the full factory image directly from Google's server. This is build LYZ28E, the latest one available specifically for phones with T-Mobile SIM cards.
In addition to the bug fixes and improvements that come with Android 5.1.1, this update includes Wi-Fi calling for T-Mobile, allowing customers call access in places where service is poor or missing. It's a functionality that's so far unavailable on vanilla builds or most custom ROMs. If you just need the much smaller OTA update, check here for a download link.