Oh my gosh!! That's COLD!!
The only people I know in this area that did not lose birds last year from that cold stretch had heated barns for their chickens. Loss is expected in extreme weather, but I think you are right in thinking about how to minimize the impact. I only have 10 birds, so a little Cozy Coop heater in the coop might be the difference in saving a hen or two, I hope.
The other thing I look at is the cost. Running a Cozy Coop heater at 200 watts would cost me $0.48 per day, or $6.72 if run continuously for 2 weeks if we get another extreme cold stretch like last year. To me, saving a bird or two would be worth the cost of running the heater.
But I do think it is better not to rely on any heaters, if possible. There is cold, and then there is extreme cold which I believe many people do not understand unless they go through a tough winter with their animals. I just don't know at what low temp a supplemental heat would be best for my chickens. For example, should the chickens be able to survive a stretch of -30F without a heater, or should I add supplemental heat at that point? I don't know as this will be my first winter with laying hens.