Although many of us who travel regularly know who operates particular routes and have a rough idea how ticketing works for the less frequent traveller (or even a frequent traveller on an unfamiliar route) there's a lot a traps that can end up leaving the customer annoyed and out of pocket.
I was reminded of this earlier today when I noticed a Tweet from someone who was taken by surprise when they purchased a ticket from a Virgin Trains East Coast branded ticket machine, boarded the first train to their destination and then were charged for a new ticket on board as their ticket was for Great Nothern only.
Not everyone is aware that rail ticket retailers have to sell tickets for all operators and therefore although the machine is operated and branded Virgin it can sell tickets that are excluded from their trains.
Those who aren't familiar with the route may not even realise 'Great Northern' refers to a train company that only serves the southern section of the ECML, as both the GN and ECML franchise has had many names since privatisation they may just think Great Northern is the name given to a route, not a specific operator on that route. It's also possible some people think GN or Great Northern might have had something to do with GNER.
As the rail network is supposed to be turn up and go and the average customer shouldn't need to know who's the primary operator on the service I think restricted tickets need a way of being more clearly identified in the system. Just to add further confusion sometimes rail operators borrow other operators trains so your Virgin Trains East Coast service may turn up in East Midlands Trains livery.
Operator specific trains have their advantages, the Great Northern services are generally slower with multiple stops so it makes sense that a passenger not in a hurry can buy a cheaper ticket on the slow train, but at the point of booking it should be a bit clearer than "Great Northern only" - e.g. These tickets are valid only on services operated by Great Northern, they are not valid on the faster services operated by Virgin Trains East Coast. I think if a machine is branded by an operator they need to make it clear if the tickets are not valid on there.
I can see this mostly being a problem at Peterborough, Stevenage and Kings Cross where services are operated by Virgin Trains East Coast and Great Northern. It may happen in other areas too where there's overlap with other operators.