I'm not sure what you're trying to say here.
Caltrain is a monopoly because there's not another competing train running alongside it that can take you to the same place.
Caltrain is a monopoly because there's not another competing train running alongside it that can take you to the same place.
Key difference: the lack of a competitor doesn't make a monopoly. The inability to compete is what makes an organization a monopoly in its space.
For local service there is also overlap with BART on the north end, and with VTA on the south end. So, there is competition.
Plus you could also drive. There are also shuttle services that are competing to move commuters, and not all of those are subsidized by employers.