What if you had holiday booked but then a course came up ? What if you had nothing immediately booked but had one planned for a future date ?
What difference would it make? If I had a holiday then I expect I would have to cancel it if I wanted to get on the course. They aren't going to wait for me to come back from my holiday. (And I don't believe courses just 'come up'). For a £6.5bn project, I would expect there are going to be several project managers poring over Gannt charts, trying to juggle resources, people, assets all to be in their various places at the correct times they are needed.
If I didn't have a holiday planned but wanted to make future plans then that makes the question irrelevant too as asking GTR for information (so we can plan our lives) results in the standard response they have no information yet.
So, I still maintain that it was a fairly superfluous question to ask when there was nothing to be gained by either side by asking it, unless GTR were aware of course dates when asking the question, which it seems they were not.