I'm sure this area is not their only account. That might cause the varying times they do come and plow.
That being said, this is a residential area and like construction start times it should have a no sooner than time. It's not a company parking lot that is closed and they have to have it done before workers arrive the following day.
For that I would be fine with no sooner than 5am. At that point if you wake up, oh well. Most people are already getting going for the day around that time.
A lot of times if they're using a machine it IS that employee/employees only account as the machine does not move off site.
Shovelers may go from site to site, but, the one guy in the machine typically stays with that machine/ property.