As far as Canadian icewine's go, I've probably had more sparkling wines than regular still bottlings, and actually, I don't think the sparkling icewine's need to be any colder than the still wines. If they are too cold, they lose some of the warmer aromas and the flavors become muted to the point that it tastes like you just have a mouth full of water flavored pop-rocks. As far as varietal goes, I agree with Board-O that I like Rieslings colder than Vidal. I like Cab Franc about the same temp as Vidal, and I prefer Scheurebe in any way I can get it because I LOVE it, and it is my favorite varietal for any type of sweet wine.

PS- has anyone ever seen a German Sparkling Eiswein?
Jester