Yup, that's the fix, although I would think the risk of spontaneous combustion can be mitigated by formulation. It doesn't happen so often that the benefits aren't worth the hazard. Further, it turns out that gas mileage on rubberized roads should be a bit better. Economically, that would be a win.
I don't know a better way to handle the problem.
That was in early days when they first allowed it, so maybe the Asphalt engineers have came up with a better formula/mix design to prevent that from happening again.