The etiquette is "first come, first served" and "no squatting" (move ASAP when full). It doesn't what type of EV it is.It wouldn't work. No Etiquette will work when you have Volts and Bolts and Leaf and Cmax all wanting to charge when the Leaf and Bolt NEED to charge but the others have gas to get home.
It just happens. Even I have those thoughts.
Like I would Gladly give up my charger for a Leaf to get charged but NOT a Volt or Cmax or any other hybrid.
I know an employer in Silicon Valley that often places charging stations between two rows of parking spaces which are reserved for EVs (i.e., if you drive front-in, the charge plugs are between the two vehicles' hoods, and both vehicles share the same plug). So they have almost twice as many parking spots as they do plugs available. Company policy is that it is OK to unplug another vehicle if it is fully charged (you have to agree to that). Also, a lot of employees put up signs that say "it is OK to unplug me if XXX" (such as "once the 2nd light indicating SoC has turned solid" on LEAFs). It works just fine. There is also an "understanding" that if when you arrive there is no plug available and you need a charge, you leave the charge door open. When somebody close-by unplugs their car, they will plug your vehicle in without you having to be there.
Of course, we are all granola-crunching hippies who are so laid back that we wouldn't even notice if anybody had unplugged our car, so ...