This morning I looked for a similar extension for Google and I've found this fork[1] of Mozilla's extension. It's working as expected so far but I'd love for it to be officially maintained by Mozilla at some point. There is an open issue about it[2].
[0] https://github.com/mozilla/contain-facebook
No.
Hmm this is a smart move indeed, all of a sudden I'm logged into G-maps whereas I wasn't before... FireFox helpfully opened google.com/maps in my Google container...
google.com has now direct access to your location, it doesn't need any cookies.
(Of course it can probably make a pretty good guess, just as well it could do before this change.)