Network Rail distributes the timetable data to all users. Technically there is no difference between the public timetable and the working timetable - they all come in the same file and each station in a train schedule has a working time plus a public time (if it takes passengers there). All the details for the train such as reservation and catering status are also in there and it all comes from Network Rail (although obviously those aspects of it would be maintained by TOCs, but Network Rail controls the standard).
The claim was that they own the data, so are responsible for any changes to its format.
Correct - that's what I meant. I'm surprised anybody is challenging that; I thought it was a definite given.
It all hinges on whether a train can simultaneously be reserveable and non-reserveable in the reservation system.
No I don't think so - the reservation status just needs an extra level of granularity. Currently there are three values:
S = reservations available
R = reservations recommended
A = reservations mandatory
What we really need is a fourth status, which indicates "counted places available".
I'd guess that there are two sticking points to getting changes made to any of the codes used in the train schedules...
a) who's budget pays for it
b) are there any of the myriad recipient systems that can't handle it (and of those, which have a safety case that needs to be re-done).
I think the answer to this is to make the changes in a backward-compatible way such that nobody
needs to spend anything, but anybody who wants to provide clearer information to passengers (whether TOC or software supplier) can do so voluntarily as and when suits them.
My suggestion would be: change the meaning of R (reservations recommended) such that it means reservations available, and change the meaning of S such that it means "counted places available". "Reservations recommended" is so rarely used that this shouldn't cause any major inconveniences. This wouldn't break anything, and although it could cause some false advertisement until all suppliers had updated their systems (i.e. advertising a train as only having counted places when in fact it had real reservations), that would be a "fail safe" scenario as the passenger would get a better outcome than advertised.