The policy is a step in the right direction, but very limited in its scope. How long do you think it will be before some of the newer plastic pipe starts having issues? In many systems it already has.
So a policy that is limited to only certain kinds of pipe material is incomplete at best.
Most systems over 70-years old were designed to allow a certain level of dilution. Now that dilution is an expensive and environmentally unfriendly problem -- don't blame the pipe materials for the state of the art when they were installed.