Pretty useless when plows clear most of the road for you. But what can you do on a regular mountain bike? You can go on roads and on the trail.

You should be able to use the ktrak on roads and in trail (snow). Couldn't you have a front tire on whilst also having dual skis (1 on each side of the tire) or a even a snowboard with a slit in it to slide over the tire? (I feel like a bike needs the extra width to float on snow) Whatever option, having it slightly higher than the tire so that if you go into deep snow, your skis/snowboard settle on the snow and you continue on.

I would also say that it's almost mandatory to have a motor but since law basically states that it must be electric, an electric motor would have to be made to work somehow.

It would probably be wise to simply have an extra bike retrofitted with these contraptions for snowy days. You would only use it on those really snowy days where snow is still on the road even after being plowed - not on those "winter" days where the roads are very clearly rideable on a regular bike. Only reason that I can think of is that you would probably wear down the ktrak on pavement pretty quickly.

Is there any reason that such a bike fitted with ktrak with a front tire with skis/snowboard mountain on the front and an electric motor that could withstand cold wouldn't work?