I've got two Nexus 6 devices. Both are on Project Fi, one with 7.0 Oct SEC and the second has 7.0 Nov SEC. I have been working with support, and they claim the update should happen at any time. I am convinced that they think it is a device specific issue, where it is actually a Google/carrier issue.
I'd be interested to hear what the latest OTA update anyone has received on the various carriers.