If they have the details wrong then the ticket is unenforcable, same goes for Traffic Wardens, if they've put down details of a non-existant car then the ticket can not be enforced. You often see this defence used in London against TfL and their bus-lane cameras (the wrong camera/unit number displayed on the photographic evidence, thus rendering the evidence/proofs invalid, along with the offence)
With regards to the pass, If the signs around the car-park do not stipulate how to display the pass then they can not use that as an excuse, they can try and refer to a service agreement or what-not but that will not wash in court as you just counter that with "and what about first-time visitors/users of the car park, how to they know how to display the pass?"
With regards to the pass, If the signs around the car-park do not stipulate how to display the pass then they can not use that as an excuse, they can try and refer to a service agreement or what-not but that will not wash in court as you just counter that with "and what about first-time visitors/users of the car park, how to they know how to display the pass?"