I used to work at a Ford dealership as a salesman, and no where did it tell us what the Fusion's AWD system was. As I own a AWD Fusion I was very curious, and dissappointed when even a salesman wasn't given the information, and our techs just said it was a computer controlled limited slip system. I live in northern Canada, and we get probably about 3 feet of snow at a time, since this was my first winter with the car, I didn't bother with snow tires and just used relied on my AWD. I never got stuck once. Stopping is another question, ABS only does so much, and AWD doesn't help stopping, so you might want winter tires to help with stopping, but with stock All-Season Micheline tires, I never got stuck or slid (other than stopping). However, due to the weight balancing (60/40) the back end does give a little when cornering in snow at 50-60 kph, but nothing too drastic.
I hope this helps you a bit.