I never have, but if it were even a request, i would figure out a way to get it done. Last time it snowed here was three or four years ago, and we got a trace.
I just charged by the hour per man with a minimum trip charge. I think the whole job was $250-350 and we did all the trucks that had the snow on them about 10-15 I think and travel was about 45 min each way. They were very happy with the work and it was a lot cheaper than a ticket or a broken windshield from the ice flying off that formed on the roof.