I suspect that like most airports, there's a price list for all of the ground handling service options, and the operating airline can choose what they want to pay for. Obviously there is a shortage of contact gates but pay enough and you can probably have one. Separate buses, priority baggage handling and fast track security, etc? Cough up Mr/Ms Airline and they're yours. That's not to say some things won't be deliberately priced high to throttle third party demand of course.