I have zero knowledge about this thing, I know as much as you do. I can talk all day about the payments ecosystem though. :)

Google does publish a bit how they handle data requests.

https://support.google.com/transparencyreport/answer/7381738...

There was an article a couple months ago about reverse location search warrants.

https://www.google.com/amp/s/slate.com/technology/2019/02/re...