^ Makes sense, really. Nobody in the MU knows about the wormhole, so then they can't know about the Prophets or Pah-wraiths. And since regular-Jadzia was killed BY the Pah-wraiths...her MU counterpart must, logically, survive. Thus, Dax is still inside Jadzia.
At least until MU-Jadzia is herself killed ("The Emperor's New Cloak"). So it would seem that the mirror Dax symbiont is also dead.
Oh, wait a minute: Never mind. I did some checking - in the MU, Jadzia isn't Dax either. The mu-Dax never left Curzon.