I have done photographing down to about -37°C.
Apart from batteries, the only equipment I have that doesn't work in the cold, is my Markins ball head. That ball head freeze up somewhere between 0 and -15°C. My RRS BH-40 works without any issue at least down to -37°C.
What I allways try to figure out when I buy equipment, is if I can use it with mittens. With most of my equipment, I can.