Already very well paid the government unions realize that unlike all other businesses their bosses can just arbitrarily raise prices on their customers through higher taxes and higher fares. Additionally eco-nazism in California makes it hard to drive a car so there's really no viable competition to keep BART prices down.
The unions bribe the politicians, who never pay with their own money, by providing support, support not limited by the laws that limit contributions by other groups.
The only people who suffer are the taxpayers. Which the unions and the liberals have no problem with.