To answer your first question - no, not on a bike.
I had a 10 am meeting in Pemberton and decided to take the scenic route home - had the rest of the day off!
I asked at the Shell station in Pemberton how the road is and the cashier said very, very icy. Seeing as I only have all-seasons on the rear-wheel drive cage, sounded perfect .
The road is actually fine but very sandy and icy in the shade - and bloody cold. At one point my car showed -14C outside temp. Also, bumpy as hell - probably due to frost heaving etc. Seemed much worse than my frequent Duffey rides on the bike last year. In the shaded, icy areas, there is soooo much sand (no salt that I could see) that it is like driving on a dirt road. And where there is avalanche danger/road slide danger, there are tons of rocks on the road. A couple of times you have to come to a complete stop and navigate through the debris.
So, could you ride a bike on the Duffey in winter?? Hell yes, if you are bundled up, have a dual sport with suitable tires, a big, protective windsreen (V-Strom??)... and are a sucker for punishment. Not for me - I will wait 'til spring after the spring rains and the sweepers have swept the sand off the road.
Sure was nice to let the car stretch its legs on the Lillooet/Lytton stretch, which is in mid-summer shape! A fun drive on a beautiful day.
And not surprisingly, I didn't see any bikes at all today.