Alas, I see from the Veloteq parts list that there is no winter tire.
http://veloteq.com/pdf-files/500seri..._lsit_2007.pdf
However, the stock tire is quite good. Even on nasty ice, I just go slow, put my feet down on the ground and "walk" along with the ebike. However, as this is slow, I only do it for short distances. Generally, within 24 hours of even the largest snowfall, the city of Toronto has ploughed all the streets down to bare pavement. During that 24 hour period, I take the TTC. I'll even do that anyway sometimes if where I'm going is right on one of the subway lines.