4
I am not an expert nor do I claim to be but I am surprised based on my experience of how businesses are managed and I have more than 30 years experience of that there are no emergency plans for such eventualities but there again the railways have always been very insular in that respect
4 miles worth of sleepers and rail is not something that is reasonable to keep "in stock" locally, and the longitudinal bearers will be made to order, because they are unique to each location.
There is also the logistics of moving the materials to site, and where you offload it nearby without completely stopping access to your worksite.
It's not an overnight process.
The railway has contingency plans for many things, but the amount of damage talked of here is exceptional.