What do they do on the lines where trains are running Christmas and Boxing day?
Playing devil's advocate, I would suggest they do the same as on the lines running trains.
There are no trains anywhere on the network on Xmas day, other than engineering trains. On Boxing Day it’ll vary. Some will be lines which are four tracked such as the BML, EL on the west and eastern sections, so two lines can remain open while the other pair is worked on.
Some jobs, eg this year’s MML blockade, will require complete closure, and it’ll still make sense to schedule them over Xmas, hence no EL line, and no trains to or from Luton airport this year. The alternative would be long blockades over Easter, the August bank holiday etc.,potentially disrupting far more people in the case of airport services.
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