An even better fit than Escapes would probably be the Camry hybrids by Toyota that will come out in a bit more than a year (or maybe Altima hybrids by Nissan?). In any case, the kind of stop & go city driving that a taxi does is exactly what full hybrids (maybe even supercapacitor hybrids in the future) excel at; with high-torque electric motors that make accelerating from a stop easy and less wasteful, electric-only mode for short distances, idle-stop (engines shuts down when vehicle is stopped) and regenerative breaking cutting losses of efficiency due to the constant waiting around for lights to change and traffic jams to end.
It would also be interesting to know how many miles/kilometers a NYC taxi drives per day on average. Maybe it is within the range (or future range) of electric vehicles?
But things are not so simple since a bill that would permit hybrid vehicles to meet regulatory specifications for license by the Taxi and Limousine Commission is stalling in the Transportation committee. We'll try to follow that one and see how it develops.