In order to accomplish the oil-free goal, RATP is looking at a variety of alternatives. It already runs a third of its fleet on B30 and has plans to test buses running with ethanol and B100, as well as using Stop/Start systems to reduce fuel consumption when buses are not running.
Rail vehicles will also get upgraded. All trains purchased after 1989 have a system of electronic motor management which distributes energy better and also captures braking energy. This system is currently working in 53 percent of the métros (subways) running, 65 percent for the RER (commuter trains) and 100 percent in tramway systems.
[Source: RATP (thanks to my buddy Dominique for the tip]