It's not about ownership of the stadium but about income from it.
Look I've had a few businesses in my time and when i lease a Nightclub for the purpose of drinking and dancing and allowing the public to congregate there then I own the rights to sell the beer and make a profit not just profit from the door money. Get it?
Once you understand that then you can understand why SISU are asking for the right to revenue streams when they occupy the building on a lease term? Seems fair to me. Either that or if not, then a reduced rent as we only use it to play football on and have the public there..we are not actually getting some of the revenue generated by 'our' client base coming to your beer counter/pie counter or what ever else is inside the bloody place.
It's a bigger remit than that but that's the general idea and not an unreasonable one.