OK, for all those people that still do not believe in working batteries in cold temperatures, read this paper on Energizer lithium batteries that are readily available in stores. Yes, performance is less at -20C but these batteries are still far from dead at that temperature.

This is type of battery that I use in my film cameras. The operating range is specified as -40C to +60C (-40F to 140F). -40C is probably pushing it for the winder (high current) but the lightmeter and shutter should be fine. But I will certainly not go out for photography at -40C (excl. windchill) so that's not an issue.