It was the Tories who destroyed a lot of coordinated cross London service provision because of a dislike for its political complexion in the 1980s. They have already started trying to remove free travel for older people (by removing the guarantee for the Freedom Pass) and children on the GLA.
Also, though it was the Labour government who pushed through tube privatisation, Ken resisted it and was expelled from the Labour Party for a time on this very issue. Now Metronet is asking for more money, we will probably pay the price of a disatrous decision to privatise the tube anyway. But if the Tories win the Mayor in addition to their current strength on the GLA, do you really believe they'll stand up to companies like Metronet who believe they can get away with taking public sector organisations for everything they can?