From what I've read, Mozilla had some agreement with Google to keep all the data from their tracking stuff silo'ed so it wasn't aggregated with other data and wasn't used for anything besides showing back to Mozilla people.
and
They're now (and have been for more than a year) respecting DNT, removing the GA code so that you don't make any requests to google if you have that enabled.
Two things to note from that thread:
From what I've read, Mozilla had some agreement with Google to keep all the data from their tracking stuff silo'ed so it wasn't aggregated with other data and wasn't used for anything besides showing back to Mozilla people.
and
They're now (and have been for more than a year) respecting DNT, removing the GA code so that you don't make any requests to google if you have that enabled.