You have a point. But I'm not sure how many of the 450 million or so yearly passengers RATP has on its sections was also counted by SNCF on its part of lines A and B.

At any rate, the Paris urban rail system (Métro+RER+trams+commuters) is superior to London's at present, what's more, London looked at Paris for inspiration. The Crossrail proposal, which got a boost after London got the Olympics though won't be ready for it, and the less ambitious (but ready by the Olympics) East London Line project are modelled on the RER.

_{*Lunatic*, n.
One whose delusions are out of fashion.}