It can go the other way as well. Originally power companies like PG&E were also streetcar companies. They found that power generation was profitable, but main l

It can go the other way as well. Originally power companies like PG&E were also streetcar companies. They found that power generation was profitable, but main line transmission wasn’t. But if you’re going to do the work of building a main line into a city... why not run a streetcar underneath it and sell fares? That combination turned out to be profitable, and to be a great win for the cities. This was made illegal during the rise of the automobile, all those companies were forced to split up. This greatly weakened the transit companies and helped undo them (as desired by the oil and auto cabal).