It's all a green-washing scam and all they want to do it fudge the facts to make themselves rich. And electric buses are even worse.
I read a study that stated if everyone in North America bought an electric car, and it used a truly clean and renewable production source (as opposed to the majority coal burning electric production we have today) the lifetime carbon savings would not even cover the carbon footprint of even a couple days of current global population growth. And that's with clean energy, not coal.
Just by existing, humans create carbon, garbage and other waste, and we have overrun the Earth to the tune of 2.2X the number of people the planet can reasonably support. It's the way it is and as capitalism can only exist with consistent population growth, we're all pretty well screwed and no corporate green-washing campaign is every going to change that.