I'm guessing the people went to "A" because they held out. If you hold out, you are held to higher standard to protect the public. If they are getting dumped off on a non 135/121, their actual flight is not being held to that higher standard. Think of it this way - Delta and FedEx hold out. They can't subcontract their flights to a 91 or 125 even if the subcontractor says we only work for Delta or FedEx.