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Water has been used to improve the performance of high compression engines at least since WWII. Water as a value of latent heat of evaporation which is quite high. This means that in order to cause it to vaporize it requires a lot of energy which in the engine takes heat out of the combustion or allows a slight increase in fuel use given the same temperatures and pressures. Since water slightly cools the intake charge before combustion it allows a slightly more dense charge of fuel with respect to air because the air volume is slightly displaced by the water and since the volumetric efficiency of the engine is finite over a certain range of operation the net air amount is decreased. This causes a slightly richer mixture because a carburetor doesn't know the difference between air or water vapor. A richer mixture often prevents knocking. When an engine doesn't knock it is using the available fuel most efficiently and this is where I suspect you gained fuel efficiency. To maximize the benifits of water injection one should consider turbocharging where water injection is syncronized with increase in manifold pressure and fuel delivery. This is where high performance gains can be realized, like in WWII air craft, but not for the purposes of increasing fuel mileage. Racing cars that use methanol use it because they can increase compression up to 15:1 and cool the charge as well but unlike water, alcohol is a fuel and provides the heat needed for power generation and alcohol evaporates readily at lower temperatures than both water and gasoline.

The whispering wheel is interesting because when I was a child I was interested in hybrid cars described much like the bus is now. This was over 30 years ago. The problem then is as now but not as severe. How does one control power to the motors without wasteing energy (heat)? Before power FET's it was difficult but even today it is not without energy loss. The article describes the bus not having bearings on the axles. It has to in order to roll even if the bearings are in the hub it will have a bearing surface somewhere. PM's have been the dream of high mileage cars for years but are limited in being able to allow high power density in an electric motor. It would be interesting to see one of these busses, loaded with passengers make it up one of the hills in the cities in Northeastern USA.

While the issues of torque from a standing start, unsprung weight and cost of the vehicle's engine and batteries give me pause, I do know that magnet material technology has revolutionized that field, albeit with cost problems as well.

The thing that gives me pause is the battery recycling. I built a facility for that some years ago and I will tell you that this is one of the most corrosive processes you can imagine. Some of the actual buildings, adjacent to the process areas, structurally corroaded to the point of replacement within ten years. Even rainwater falling withing the facility became so polluted a treatment plant had to be built to process it.