If the fork crown is like the one they used in 2000, fitting a 700x37 cyclocross tire on the front wheel is dicy: it works, but with about 2 mm clearance, it won't work great in the mud. I'm aware that Continental and Schwalbe both offer 700x32 cyclocross tires and was recommended the Continental for Winter rides (except the LBS got them this Spring) and mud rides (which I don't do), because the Schwalbe is thinner and rumored to be more slippery; different compounds, I presume.
On the rear wheel, a fat 700x37 fits, and a 700x42 would likely fit.
So far, I have used throughout various winters:
- IRC Cyclocross: good tire, with a narrow smooth central section and knobs everywhere else. The gum seems hard, so it grips well in snow, but not as well as the other two on ice.
- Specialized Cyclocross: same profile as above. Great tire in all sorts of snow, sleet or ice. I suspect it uses a more "aggressive" gum than IRC.
- Specialized Expedition : very good tire. Smooth central section, but large chunks with wide separations on the sides. It's the best of the three on ice and soft snow, but not as good as the Specialized Cyclocross on (in) sleet or thick wet snow.
In Summer, I rarely ride off pavement anymore (it's hard to do in Montréal), except for the occasional trip on a gravel bike trail. However, from past experience, I would say that the Specialized Cyclocross would be great if you expect to ride in mud, whereas the Specialized Expedition would be great in all other environments... including pavement.
All these tires (especially the last two) could be used all the time. They are heavier than "typical" touring tires, so you will accelerate more slowly. They are not noisy, and with the last two (and especially the Expedition), you feel as much in control than with a narrow tire.
If you plan a mixed road/mountain tour, I'd suggest you use the Specialized Expedition, or tires with a similar thread and compound. Don't plan on carrying an extra set of tires to use on pavement. The gain will be minimal and will be offset by the weight penalty.
Regards,