@shri your building is OLD and Special and wilson that is running the car park like you said probably made a deal with the company to park as many cars/bikes as possible, wilson probably got a good deal out of it or if they refused be left with empty spaces with no money coming in.
Not all car parks will agree to these, majority will laugh at you when you ask "is it ok for me to park my motor bike in front of my car and only pay 1 fee for both" LOL