Is it possible to make fire using a lens of ice? Can a piece of ice be shaped into a magnifying lens that focuses the sun to start a fire? Will this save your life? The answer is yes and probably not.
I've come across reference to this technique in a handful of survival guides but had never before seen proof of concept. I certainly wasn't going to spend the time finding a thick clear piece of ice, shaping it into lens form, and then polishing it smooth with my bare hands. So I was fascinated to come across this video from Lifehacker, where the technique is successfully demonstrated.
I particularly enjoyed this video and was impressed by the demonstrator's facility with his pocket knife, amused by the abrupt cut from rough block to polished lens (which surely involved considerable work and skill), and enjoyed the glittering sunbeams that reflect through the lens when he first shows it.
So there you go. You can make fire from ice, evidently.
Is this a useful survival skill? No.
The vast majority of survival situations don't occur under clear sunny mid-afternoon skies when you are healthy, warm, and otherwise comfortable. Survival situations occur when it's dark or getting dark and you're cold, wet, and/or injured. Also consider the fact that the sun must be sufficiently high in the sky to produce enough heat to start a fire. In winter--when ice will be around--the sun is often low in the sky, even at its highest point of the day.
So my take on this technique? It's a very cool winter camping party trick but I would recommend focusing on learning more useful survival skills instead.