If the idea is just that Facebook employees should be polite and well-mannered two other types of workers in the building that makes sense.
Edit: I just don't get where the line is. If FB uses ChemLawn to fertilize the grounds, are they also responsible for those workers wage rates? What about the HVAC crew, building maintenance (assuming they work for, say, Smith Building Maintenance) ? If ADP does their payroll is FB responsible for those employees wage rate? Security guards? These food service employees work for a company that provides food for more than one company. I just don't get it. Why isn't their actual employer responsible for their wage rate?