I couldn't say for sure, but here's my thought. There's not much room for water and ice to collect, meaning there won't be MUCH ice on there. Thin layer, sure....Not saying there won't be any, but......When those blades hit the deer, I'm thinking it will bust what small amount of ice there is and work perfectly fine.

Did you try to open them after you froze them? If so, how difficult was it to "bust" them open?