A good question that I have never had the opportunity to test .
You will have 3 problems.
1. Finding a contractor that has not done the annual maintenance and parked up for winter his mower, hay rake, baler and wrapper.
2. Having enough good drying days to get the grass moisture low enough to make firm balage. Balage made wet does not stack well, is very heavy, and smells smellier.
3. If you are in a place that is getting frosts now, the inoculant may not work fast enough to beat the bugs that cause rotting. Your contractor will need to use inoculant.