This probably isn't what you want to hear.
In my misspent younger days I did a lot of winter riding both on and off road. It was a mix of trail riding and racing where I competed in and won winter enduros in New York, New England and Canada in temperatures down to -10F/-25C. Altogether, I would say I've done around 5,000 miles in winter conditions like the original poster wants to ride in. In those days I used Bridgestone full knobbies on Honda 125's and an Ossa 250.
The Bridgestones were our all year tires and the compound was soft and the tread was aggressive enough to give a good balance of traction in snow up to a foot deep as well as on dry roads at speeds up to about 60 mph/100 kph. Our decision to use them was based on the fact that they worked the best in the soft gooey clay we raced in in the warmer months. For what it's worth, we used our old worn out tires because the sharpness of the knob edges didn't seem to be as important in snow as it was in mud. I can't remember what we used for tire pressure, but it was a bit lower than what we ran in the other seasons, probably somewhere around 20psi/1.3bar.
As far as engines, the low output and power curve of the Honda was ideal in helping to prevent the rear wheel from breaking free on acceleration. The Ossa with it's huge low end torque was nice in deep snow, but on the pavement you had to be extremely careful with the throttle to prevent breaking the rear end loose. Breaking the rear end loose on packed snow or black ice meant you were going down, no ifs, ands, or buts, you were going down.
From my experience with my K75RT, I would say that there is no tire available that would work in the slightest amount of surface frost. The RT with that huge, heavy fairing is horribly top heavy and the steering geometry of the front end does not have enough trail to make the steering stable enough. Bottom line, in winter conditions with frozen surfaces an RT is an accident waiting to happen and it won't have to wait too long.
My advice is to put the RT up for the winter and get a lightweight bike in the 175cc range and concentrate on windproof clothing to avoid the effects of wind chill.
