I don't know about the aircraft but my limits for enduring the cold were always hit first, normally at about -20 C still air.
One of the types of aircraft I had the pleasure to fly in the Artic peformed very well once you got it up and running but that was just the thing we had minimum temperatures for starting engines to ground idle (-26 C or more indicated temp of the engines, my memory is a little bit hazy here, I think this was an oil temp prior to start springs to mind) and then limits for setting them to fly (again -10 C indicated temp, possibly oil temp) I never saw temps this low as we hangared them in heated hangars at night.
There were a whole load of other factors concerning the transmissions too. I never came across it but we had to change the oil we used once we went Oop north because of something called coring and the reduction of viscosity of the oils and subsequent lack of lubrication which could lead to damage and overheating of the transmissions.
As I say the crews limits were always hit first either cold fingers and feet, hunger or that bladder caption again
