Someone I work with said he got the spray (in the US) and that it did work on the 407 but you never know if what people say it's true. When I didn't have a transponder, I did see a flash happen when I went by the toll on my car, it does not if you have a transponder but it does if you don't.
Also remember there are "products" that claim they work against photo raadar and red light cameras. One of which is a spray that reflects the camera flash as well as at least two plate covers. But the 407 cameras do not use a flash. I confirmed with the sole Canadian dealer, (which is in Calgary). He confirmed that these products do NOT work for the "Ontario toll cameras" Just in case anyone was considering these as an option...lol