Years ago when I was running cranes and driving trucks we had block heaters, propane heaters and circulating hoses on all the trucks and cranes. Usually we didn't have access to power so the propane heaters were run all night long then we would show up an hour early so we could hook up the circulating hoses to the pickup engine to warm up the equipment engine before trying to start it. It usually only took about 15 minutes with the circulating hoses to have the engine warmed up to a startable temperature.
The problem with the propane heaters is at times the wind would blow out the fire so we couldn't rely on them. Also, while we were warming up the engine with circulating hoses we would also hook up battery cables to warm up at least one set of batteries.
I can't remember ever not being able to get the equipment started. There was one time though when it took all day to get them started. Mid day the superintendent came out to check on our progress. I apologized for it taking us so long. He said, no worries, his thermometer showed it was -60F but it may be colder due to that is as low as his thermometer goes.