I think the testing is still up to the mfg, but there are some independent institutes that may check it (and EcoModders as well
). There will be more testing and checking as this starts to get more and more important.
I don't know anything about track or 4x4 tires.
I've noticed that most articles on low rr tires (including this one) comment that lower rr reduces grip and braking efficiency, but only once have I read that those are two different animals: Rolling resistance is mostly from the tire wall flexing, while grip depends mostly on the type of rubber used in the tread. Of course, tread pattern has an effect on both, and decreasing sidewall stiffness can improve grip while increasing rr. If a tire is reengineered to have a stiffer sidewall, good tread pattern and soft rubber tread (all in the right proportions), then it will have lower rr while retaining safety and handling parameters.
Or you can just pump your tires and drive slower