We will wash until about -6 C if it's not snowing. Usually if the sun comes out for a bit the ice will tend to evaporate off the trucks for the post part. Sometimes we will spray a bit of wd40 or lock deicer in the locks but aside from once I've never heard about trucks being frozen to the ground or having their brakes frozen. The once was a company with 40 vans that insisted on washing when it was -12 C overnight even though they were warned. Apparently upper mgmt was coming so they wanted everyone frozen out of their units in the morning!