If I'm reading that right the Battery Electric busses had the lowest maintenance costs? The need to charge is a potential issue, but at the same time busses do lots of low speed stop and go where battery systems are most efficient. As long as the bus has enough capacity for an entire day and can be recharged overnight it seems like an ideal solution, minus of course the up-front cost of the bus. Lower fuel costs, no noxious pollutants, less noise, lower maintenance, there is a lot to love.