From what I can tell, it IS front wheel drive to facilitate a low floor, high ceiling, wheelchair access and kneeling function. It's like a really big minivan I guess and in a few pics you can see the driver is a step up which is how the engine and transmission fits. There was another thread with the same bus on offer and a pic which included the underside which from what I can tell the driveshaft sends back up front into the front axle.
In any case, it would be a bit of a unicorn so you'd be hard-pressed to get much help in a conversion. I may also be overly conventional but the single rear wheel design may prove a limitation as you begin adding the weight of a built-in interior, holding tanks, batteries, etc.