London Underground responds, but where is Tube Lines?

Last week, I emailed London Underground and Tube Lines, as reported in the Hendon Times (if you click the link and scroll down) about the planned programme of weekend closures on the Northern Line. These closures will enormously inconvenience passengers and there are surely other ways of doing this work. I called for the release of Tube Lines' "optioneering" document - the document justifying Tube Lines' decision to go for this option, rather than other options which could include fewer weekend closures. I strongly assume that such a document exists, based on my own experience of working for a utility company. London Underground has helpfully replied and that full correspondence is here (here also is London Underground's Current Northern Line Closure Programme, which they have sent me). But I have yet to hear from Tube Lines; I have copied them in to my emails to London Underground and would strongly request a reply soon. Tube Lines must treat London Underground's passengers as their passengers. We deserve to see all the options that were considered when Tube Lines was planning this work. Tube Lines must publicly justify their arguments for these closures.