Switching carriers will not make it update. Your phone is on an ATT build and until an update for that build is released your stuck with that build. Unless you side load the TMO version.
OTA updates take your phone from a specific version of Android to another version. LMY48Y is an AT&T specific version of Lollipop, and AT&T is in control of when that version of Android gets an OTA to Marshmallow. Once your phone has a carrier-specific Android build installed you are at the mercy of that carrier - switching to a different carrier doesn't help.
Correct but you need to go up and read what i was referring to. My response was to someone with an ATT build, who switched to TMO and wanted it to be updated. Since ATT has not released an update to their build he is still stuck on a carrier version. Prior to 6.0.1 there were carrier builds.Their is no t-mobile version only anymore. The 6.0.1 update is for all builds. Sooner or later att will stop being idiots and let it go through. In the meantime you can flash image from Google servers which is the same image for all nexus 6 now. It is now unified.
Posted via the Android Central App
My T-mo Nexus 6 just got updated to build number MMB29S. It was a small security update I believe. I do not see anything new or different.