Exactly. Just like concessions at fairs or festivals are handled. Either there needs to be private space to park the trucks or a way to bid for the space. Using public space for commerce free of charge basically means the owner getting an insane discount on some of the most valuable real estate in the world.
When parking is free, drivers are also getting an "insane discount." If drivers can park for free, food trucks should also park for free - but the best solution is that nobody parks for free.
