It would make a lot more sense to deploy, say, ice-capable military ships
These kinds of criticisms seem to assume that Canada is doing this because it plans to base its entire defense on fleets of stealth snowmobiles. Canada is still acquiring new ships, attack aircraft, AFVs and the like. In fact it's spending billions of dollars on such programs. The question is whether spending a few million mre to investigate the potential of a stealth snowmobile makes sense given the marginal contributions such a weapon might make toward the nation's defense.
The Canadian Army already uses snowmobiles, presumably because it finds them practical for the missions they must prepare for and the conditions they must operate in. A few million dollars to test the potential of a quiet snowmobile seems very reasonable to me, and I'm a left-winger with little tolerance for corporate welfare for defense contractors.
A unit cost of $620,000 for a custom-designed, hand-built engineering prototype just doesn't seem all that extravagant to me. That might be too high for a production vehicle, but when you add up the cost of a team of engineers, mechanics and artisans it'd be very easy to spend a million dollars apiece if you're only building two or three.