According to Proterra, a Burlingame, Ca.-based company, its zero-emission electric buses can drive a stunning 350 miles one charge — and on city streets, no less. With that kind of claim, it’s no wonder investors just poured $140 million into the outfit, which began garnering heightened press attention last year but has been quietly working on its technology for the last 12 years, raising a previous $150 million in equity and debt over that period. Among its