A: It is possible that you are causing overspray to deposit on cars, even though you are over a mile away. I have worked on a similar case in which overspray traveled over one mile before depositing; however, generally only the very small particles can travel that far. It is also quite likely that the body shop is the cause of their problem.
You would need to perform some tests and a paint analysis refute the person's claim. If you need further assistance in this matter please get back to me.