This is one of the things I'd like some official clarification about, but no such info seems to be available.
I, however, think that experience is experience no matter what kind of server you get it from and as such, XP's should accumulate on unranked servers as well. I've got the impression that this is the case, too. I think I get (and lose) XP from both ranked and unranked servers.
Then again stuff like total public K/D ratio should not be affected when playing on an unranked server.