When in doubt, I go with experience. The Finns know their snow and ice.
As for 6" deep, this is another case where bikes are better than cars.
I can clear almost 8" before I'm dragging the lower RD pulley, and 10 or 11" before I'm dragging the BB through the snow. At that point it does overwhelm the motor output, so I just hop off and cyclocross carry the thing.
Try that with a Miata!
Of course, a fat tired MTB would float over the snow. But if it's that deep, they've closed work so I can stay home.
I was running a kenda kinetic in a 2.35 previously during my winter rides over the last few weeks. I found them pretty much useless in a wet snow.
Now i am currently using a panaracer 2.1 because of the softer tire compound, If i can't make these work i will have to bite the bullet and go studded.
Trying not to spend $200 on tires though, because i am wanting a brand new bike come the spring.