It is my understanding that the Heavy designation is assigned by weight only.  I dont believe that these "grayhound bus charter flights"  are designated as "heavy" and therefore the 3 minute delay requirement does not apply;  although its beginning to sound like a pretty reasonable requirement to apply when departing behind any large aircraft. 

Appreciate your interest.  thanks,  Bill Hogarty

Bill,

 

You are wrong.  Read the AIM.  Heavy= no waiver ever never by no one, not even God.

Large (over 12,500 pounds) ONLY the PILOT can Waive the 3 minutes -- NOT the tower.

 

I want everyone to understand this - Let's not have a repeat IF the tower request came before 3 minutes.  Otherwise, we must learn that rules are the MINIMUM requirement.  Feel uncomfortable, don't do it.