Unbelievable Jeff!
In short:
1) DfT (or other funder) tell TOCs what to run
2) TOCs work out a timetable, and send it to NR
3) NR collect all TOCs timetables at the same time, put them all together, and make changes as necessary to make it all fit, then sends it back to TOCs
4) TOCs check it over, perhaps make some minor suggestions back to NR if it doesn’t affect anything else
5) NR publish the timetable.
If Step 1 is late, everything else gets crunched up, and the timetable isn’t of such high quality. If Step 1 is really late, everything else runs late....