Typically house-builders do pay towards the provision of public transport in London, don't they? E.g. the current Northern Line extension
The Northern line extension (NLE) is estimated to cost £998.9m based on completion by the end of 2019. The Government confirmed in the Chancellor’s 2012 Autumn Statement that up to £1bn of borrowing from the Public Works Loan Board would be available to the Greater London Authority (GLA) to finance the construction of the NLE.
Whilst the borrowing will be undertaken by the public sector, the funding to repay this borrowing will come from the private sector in the form of:
• Incremental business rates generated and retained within a new Enterprise zone; and
• Developer contributions, raised by the London Boroughs of Wandsworth and Lambeth on the Battersea Power Station site and across the wider Vauxhall Nine Elms Battersea (VNEB) Opportunity Area under the Section 106 and Community Infrastructure Levy (CIL) regimes.
http://content.tfl.gov.uk/nl-factsheet-i-web.pdf
(my bold)