This is a nonsense delineation in systems thinking. That the railroad shareholders are also the public doesn't justify ripping them off.

Unions are beholden to the same impulses towards monopoly and rent-seeking as corporations. Swap members (i.e. sellers of labour) for shareholders (i.e. sellers of capital) and employers (i.e. buyers of labour) for customers (i.e. buyers of goods and services) and union management starts looking remarkably like its corporate analog, churning undifferentiated workers into a differentiated block of labour as truly as a mill grinds a forest into houses.