The black certainly helps give the window line more shape, which I think is needed around the front as the vehicle's design is very simple and straight-lined compared with products from the bigger or more popular bus manufacturers.
I initially wondered if the black along the sides towards the rear was to give the window area a more unusual shape, with the road-strips* then placed on top of the black. But if that was the case why would the black line go through the wheel, as windows obviously wouldn't. ...Unless they were to fit whose weird body panels that cover most of the wheel and make it look like the rear of the bus is almost floating!! Haha, maybe not.

*or maybe slightly altered road-strips to look like electric volts.

Who knows, I'm sure we'll find out soon.