Doubt there is anything for a bus like this, but if you look at a Prius there is quite a bit of data on the maintenance costs.
The rengertice breaking saves on brake pad wear, to the point that Toyota reports they don't need replacment till 100,000 miles. The Power Shift transmission has fewer gear sets, resulting in less wear on them, and has no clutch, CVT belt, or torque converter. Plus there is no timing belt, alternator, starter. And since the ICE is not running all the time it's experiences less wear and Toyota reports you don't need to replace the coolant till around the 8 year mark.
Of course this is countered by the lump sum of the battery and expensive dealership rates for when repairs are needed; but this wouldn't be a comparable factor on this kind of bus since you'd need the manufacturer to repair it regardless; and the poor MPG the old ones had would more then makeup the cost of a replacement battery years down the line.