The plotting rule is buried in PansOps somewhere; a Check Captain showed me the excerpt several years ago, but I don't remember the exact reference.
Unfortunately, the rule had not been updated to consider GPS equipped airplanes, so a lot of the rationale behind it is obsolete...
While I believe there is still value in plotting the NATS tracks, I believe it is useless on established routes such as the NOPAC and US-Hawaii routes when the airplane is equipped with GPS and FMS.