Wonderful article! I can only add my perceptions from the other cities/transit systems in my experience. In the late 70s/mid 80s I lived in Chicago, which also has an extensive subway/elevated system. At some point, the Chicago Transit Authority decided to standardize and update their bus and subway signage to Helvetica--staid, simple, easy to read. The station signs were (and still are) at every other pillar, but high enough to be read from the train window.
I now live in San Jose, home to the Valley Transportation Authority (VTA). There's no subway here, just a light-rail system. The signage is even more laid-back than BART's; it was inlaid into the tile festooning every third or fourth pillar, and you simply can't see it unless you stand in front of it. The train operators do generally tell you the next station (if you can understand them); the one automated announcement at every stop is a female voice intoning, "The doors are closing..." And so they do.