As I explained a little earlier, fuel cell buses are electric buses: you merely replace the batteries with fuel cells. All the traction system in the bus is the same.
The problem with fuel cells is with the hydrogen in them. Once you put hydrogen in a bus, you cannot put the bus into our depot. In Montreal we have seven very huge depots. It's quite simple; it's a problem with the electricity on the ceiling. It has to be explosion-proof. You need have to have special detectors, you have to even have some part of the roof or the wall that can be blown off, if there's a problem. Our huge depots were never meant to have these inside.
Also, the way the hydrogen is produced, it's not that clean. If you look at the bus itself, the bus produces no pollution at all. But you have to know that hydrogen is produced by natural gas. It needs energy; it's not zero-emission, when you look at it.