when a driver of a higher run group drives in a lower run group.... the rules of the group that he is now driving in apply.
For example... You ride with your instructor in his car in the instructor group... and the instructor group rules apply... that of usually being able to pass anywhere at anytime.
Your instructor drives your car in your run group... he has to follow the rules of your run group.... whatever rules of point-bys and passing zones for that particular run group have to apply to him as well.
As long as the run group rules are spelled before hand... it should be pretty good day for all.