I don't know how complete it is, but it seems to list cars, billboards, and speed traps. I think people are still updating it? If I come across anything better or different I'll be sure to let you know.
Edit: Oh it looks like you can filter what you're looking for. Just change the filter to Jackspots. I still don't think it's finished. But if you keep an eye on it, I'm sure it will be soon. I know there was an interactive map on IGN for Forza Horizon that was filled out REALLY fast.