I plow commercially with a PT425 and PT1430 in the Minneapolis area. The machines are kept in the shop at about 40 degrees. I would not trust either machine to start in 10 degree or less weather if stored outside unless I had some sort of heater and battery charger.
When I go to plow I just start them and go. No need to let them warm up when starting at 40 degrees. I have run them in -20 to -30 degree temperatures just fine. Leave them running while running the route. I run the same hydraulic oil and engine oil year around. I run a hydraulic plow on the pt425 and there are no issues with the hydraulics in sub zero weather.