Is it not just a bus service, that happens to terminate at a car park?
Extend it to West Rainton or Langley Park and its no different to owt else.
Its just a service operating under contract/tender, like the 82/83 are on an evening.
If it was an entirely private set up, such as the Airshow or Enchanted Park services - then I could (maybe) understand why passes weren't accepted.

I have seen passengers get off at Belmont P&R and cross over to their homes in Carville. Essentially using it as an alternative to the 20/20a.