I think the OP is asking whether the windscreen company can be made to fix the rust.

If that is a question, I'd say a firm and emphatic NO.

Paint doesn't tend to blister on sound metal and while the fitter may have disturbed it in the course of getting the window changed, it's not his fault that the car was rusty. If anything, he may have done you a favour by exposing the problem before it gets much worse.