love my pugsley.
for pure icy road conditions, yes, studded tires are the ticket... have not tried them on the fattie though. bought nates last year, what an improvement in the snow, mud and slop.
for a couple of inches or road riding narrow cross tires can work pretty well. i had 35 nokians on my crosscheck for awhile. liked riding fixed with those.

ran 29r nokians studded on my single speed and fargo, they work pretty well - but they don't come near being as stable as the fatties in the ruts and chop and certainly don't have the float.

i have a krampus in the stable now with 29x3" tires. will see how they do in the mid depth snow.