I just found this out there in the ether.
The update to version 5.0.1 should fix this MMS problem.
"Those waiting for the Android 5.0.1 update on the Nexus 6 can expect it to arrive soon, and this morning we received a full set of details regarding when that may actually happen. All Nexus 6 owners can expect something similar to the details below, but this information comes from a change-log for the Sprint Nexus 6.
According to a Verified Sprint Employee over on Reddit, the Nexus 6 Android 5.0.1 bug fixing update is set to be released starting on December 15th. He suggests the roll-out will start slow with 5-10% of users on the 15th and 16th, then Google will gradually release Android 5.0.1 for the Nexus 6 to more users over the course of the week. Stating that all other Nexus 6 owners will get it from December 17-19th.
The update to Android 5.0.1 Lollipop for the Nexus 6, and most other Nexus devices, will bring an array of fixes that have plagued the initial release. These release notes are specific to Sprint, but likely most of these will be for all Nexus 6 owners as well. We’re hearing on 4G LTE it sends double text messages (Sprint only) which will be addressed, as well as some other minor issues."
Fixes/Enhancements:
Android update to assure all Google applications can be installed properly.
Enhancements to device call stability.
Fixes an application install issue.
Fixes modem issue.
Software version: LRX22C.
Good news, I think.
Mav.