Traditionally when the industry was still at contractual timescales, public timetable information was (broadly) available at T-12 weeks. This required detailed timing and draft rolling stock diagrams to be complete, and a reasonable idea of the traincrew diagram principles, but it would have been very Unusual for crew diagrams to actually be complete by then. By its nature Crew diagramming is the end of the planning process (followed by actual rostering a few days before) so it’s subject to change until every single last detail of timing and rolling stock is nailed down.
So to my understanding on a good week you’d typically get passenger timings for T-12, stock diagrams for about T-6 and crew diagrams at T-2. Rosters were published a few days beforehand, complying with minimum legal timescales for notification etc.
Currently with seriously compressed planning timescales this isn’t being achieved but the underlying processes are the same. So you might get timings at T-8, stock diagrams at T-4 and traincrew at T-1, with rosters published at the minimum notification dates. Of course similar would happen in the past when late engineering work (or cancellation of work) was announced, at which point the TOCs were in damage control / all hands to the pumps -mode.
Addendum - with strike dates it’s the ultimate nightmare for planners, as the minimum 2-week notification period provides an extreme lack of time to properly compile the plan and diagrams. Typically these processes are forced to happen simultaneously, which creates errors/oversights, and they are being sorted out until the last minute. This is why strike date timetables get released so late in the day, as anything that is advertised in the public domain could theoretically mislead the travelling public if it subsequently changes after they’ve planned their journeys.
