The SF bay area rail and transit system seems to be a good argument for an eventual unified transit authority that will combine BART, Caltrain, etc. – undoubtedly adopting the worst features of each system in the process.
I say cacophony because there are bus', cable cars, vintage light rail, modern light rail, subway, tram, local neighborhood shuttles, and I'm sure I'm missing a few.
[1] https://en.wikipedia.org/wiki/Montreal_Metro#Station_design
One major benefit vs a shared authority is if someone wants to pay less into it and someone else wants to pay more, it is hard to get the two sides to work well.
Look at New York MTA where the LIRR and Metro-North have had the same owner as the subway since 1968 and yet there is no combined way to pay or integrated fare.