If a revised programme of works has been negotiated and an October 2012 to December 2012 delivery period for the works has been forecast, has LB Lewisham ensured that an appropriate Minor Closure Notice has been secured from the Rail Regulator by the operator.
If the underpass is deemed to be part of the operational railway and forms part of the station lease there is a statutory obligation to obtain such notice, even though the closure may only be temporary, in advance of the works commencing.
In the past successive Regulatory bodies have taken a dim view of failures to apply for such notices and have punished operators with the application of statutory penalties with cessation of works instructions being issued.
I believe it remains the case that this would be a statutory offence and not a softer "civil liability" issue.
Of course if the underpass is not part of the operational railway no such notice would be required.
Is there any web-site where an updated plan or scheme for the proposal can be viewed.