Google Support / Engineering came back to me with a 'solution' to enable video footage from a Nest Cam when Nest Protect detects smoke.
Their 'solution' was to enable the microphone on the Nest Cam, and when the Nest Cam hears the sound of the Nest Protect alarm it would trigger a recording.
I guess that could be interpreted as a 'solution' by some, but doesn't really integrate in the way the Nest 'Works with Protect' was designed. in the Nest App it says:
"Your Nest Protect can work with your other Nest products to help keep your home safer during an emergency."
I guess any brand of smoke detector that makes a alarm sound could be used in this way, and any smoke detector could be labelled as 'Works with Nest' 😂
@Brad why did you remove the link to previous post? As this has the details of original issue, it would make more sense to leave this in so others can follow the thread, otherwise it makes less sense?