Here's my prediction: In most cases it won't be enforced. But one or two TOCs (and if I had to guess one, I'd go with FCC!) will decide to enforce the rules, as apparently they are 'entitled' to, the RPI won't show any common sense and treat the passenger as if no ticket was held, the passenger will go the Press, the TOC will back down but not before the rail industry's image has been further tarnished.One set of my own Olympics tickets was "lost" by Royal Mail and I've seen Thomas Cook telling lots of their customers that they have been unable to send out tickets as promised. In all these cases, tickets now have to be collected at the venue.
How then one is supposed to produce a Games spectator ticket to show on the train on the way to the venue I do not know.
It's entirely foreseeable, so I have no sympathy for any TOC that does this, when they inevitably get negative media attention.