The manufacturing process for the bus body is the same whether it is an e-bus or a diesel bus. The environmental impact differences are in the “fuel” source.
Modern EV batteries are very similar to batteries found in cell phones and other household devices. The most common chemistry, Lithium Ion, includes common elements such as lithium, nickel and cobalt. Cobalt has a poor reputation as a lot of supply comes from conflict zones and is not mined responsibly. Steps are being made to reduce the amount of cobalt in lithium batteries and some buses use lithium-Fe which has no cobalt. Tesla and Panasonic are close to eliminating cobalt from their batteries. Canada is rich in all the metals required for battery production, including cobalt.
Unlike lead acid or alkaline batteries, Lithium batteries are non-toxic and can be disposed in a land-fill. Battery recycling is a developing industry and it is now possible to recycle Li ion batteries economically.