I have set up 7 different calendars in Google. 1 personal, 1 shared (actually its my wife's calendar who shared it with me), and 5 external calendar feeds (holidays, week numbers, etc) and all of them are synced on my N9.

First I enabled the sync of these calendars from iphoneselect page. Then I just created a CalDAV account with username and password and input the address only as "google.com". Everything works. I am not sure if this is some regional thing but give it a try. I have disabled the Calendar from MfE account. I use it only for contacts.