FWIW, when we picked up our XC90, it had the hitch installed at the FDC. Somewhere, I have pictures of the car at the FDC with the hitch installed.
Now, that was a couple of years ago. Things may have changed. Also, the answer may be different for different models so I would suggest don't assume anything and ask the people at the FDC: they will know for sure.
And even if they give you a positive answer today, please remember that things may (and do) change at any time and without warning. Don't get upset if the hitch is not installed when you pick it up -- they may have a reason (which is probably obscure for most of us).
Worst case scenario, it will be installed at the port when the car arrives. This is no big deal though as they (the port handling people) seem to do a much better job at hacking the bumper (for the XC90) than most dealers, probably because of the number of installations done by one or the other.