(This first bit is based on info we got first, about there being two clutch packs in the rear and torque vectoring, read below from the EDIT onwards for the updated theory following info that there will probably be one clutch pack to send power rearwards and one for the rear diff:)
I guess Ford is not going to tell anyone the details of the AWD system yet. But interpreting what they said at the reveal, it seems to have a driveshaft to the rear, that sent with a rigid diff(?) towards both rear wheels where there are multi-plate clutch packs on each side. And the drive to the rear has taller gearing than that to the fronts, which is how it can send more power to the rears and provide sustained power oversteer (which they claim is possible due to the AWD system).
So the clutch packs engage the necessary amount for each rear wheel, with 50/50 bias not being fully closed. Ford says up to 70% of power can go to the rears, so I guess that's possible with the overdrive ratio for the rears, with the clutches fully engaged. For cornering it regulates the clutch packs in order to not work like a locked diff and let the tires rotate at the necessary speeds, and in addition
It provides rear-biased drive by going over that front drive ratio threshold with the clutch packs. And and side-to-side torque bias by closing one side's clutch pack more than the other.
So it's like the many electronically controlled multi-plate clutch pack rear diffs that are on the market mixed with some principles from the Ferrari FF's front gearbox.
That's my theory based on what we've been told.
Ok, so now I have heard from many sources that it has one clutch pack to send power to the rear and another for torque vectoring at the rear wheels. So that means that it must have a driveshaft to the rear, and an electronically controlled clutch pack before the rear diff just like modern Haldex systems. But this one probably has an overdrive gear ratio for the rear drive, meaning that fully closed the bias will be 30/70.
Then at the diff there is another electronically controlled multi-plate clutch pack somehow juggling the drive between the two sides. Usually this kind of rear diff torque vectoring is done with two clutch packs, one on each side AFAIK. So this one apparently just juggles the available torque from side to side, and the 'vectoring push' is achieved with the overall rear drive's higher gearing compared to the front drive. This means some pretty nifty calibration and interplay between the two clutch packs...
But I could be wrong. It'd be better if Ford would just tell us what they have in there.