In the US, a more credible / stronger antitrust case against National City Lines in the late 1930s might well have forestalled the conversion of any number of largely-electric city transit systems to buses during the 1940s and beyond. Baltimore is a classic case: NCL bought the Baltimore Transit Company after World War II, and with the collusion of Henry Barnes, the transit commissioner of the day, sought to eliminate streetcars in favor of buses (that's a long story made short). Without that move, likely at least three of Baltimore's streetcar lines would have lasted into the 1970s, with perhaps a subway/surface system in place today. At the same time, probably trolley coach operation would have been expanded significantly, and said network would be mostly intact today.
There, by the way, is an interesting wank: had a consortium of transit operators, Ohio Brass (the key supplier of overhead hardware), Pullman-Standard, ACF-Brill (two key TC builders, with many others not mentioned) been formed, it's not entirely out of the question that an analog of the PCC car for trolley coaches might have been formulated. Had that happened, quite likely trolley coaches would be far, far more prevalent in North America than they are today (wherein only Boston, Philadelphia, Dayton, San Francisco, Seattle, and Vancouver still operate them, to my knowledge; I believe Toronto discontinued them in 1998).