“engineering works” nearly always mean “extra fare”
Whether it’s statutory or a gesture of goodwill, from my experience, TfL CS will virtually always refund any differences in cost incurred as a result of engineering works. I have even successfully received a refund of the differences (with no arguing needed) for making an illogical journey involving buses in the middle of what would sensibly be a single rail journey, as a result of an engineering works closure.
Edit to add: side note, you’re not going to Harold Wood for the B1 extension, are you?
