I'm from Winterpeg Manisnowba as well, and ride into the -30's on occasion.
Regularly ride in the -15 to -25 stuff.
I ride MTB's though, I don't think those road tires work very well on snow/ice covered roads.
I have Nokian studded tires that make a world of difference, I can ride on the river trail no worries.
In real cold weather -10 to - 30 and below there is no worry about deraileurs, especially with your
friction shifting. It is when you get just below freezing and the slush hits and freezes around the RD and cables that there can be problems.
But when that happens I just don't shift gears, so it is no issue.
As far as clothing goes, I am trying hi tech stuff this winter (tight fitting hi tech fabrics) that should be good to
-15 to -20. I am sort of tired of getting dressed in bulky ill fitting stuff, it does the job but is just so clumsy.
The only thing that I might go bulky on is the boots. I have some nice answer kashmir's cycling specific boots, but I need covers
(which I haven't got yet) to go below -15.
But my rides are usually in the 1.5 to 2.5 hour time frame so that's a lot of time to get cold in -20 with a strong Winterpeg wind.