Great, since the shareholders of these companies are also involved in shutting down the rail network since they refuse to give a humane employment contract, you should be equally unsympathetic to their side. Since all else is equal on who should be blamed for shutting down rail or the economic impact this will have, then should we not be preferring the side that has the better ethical claim?

This is exactly why a strike is devastating and the point of the talk about Congress intervening. However, if it goes down like the air traffic controllers in the 1980s, their labor monopoly may be broken while the rail monopoly remains intact. So again it creates an asymmetry in power which is why taxing the employees is wrong-headed.

Tax the companies and they will adjust their rates, pay, and dividends. Tax the employees under a monopolistic employment, all you'll do is make the pay absorb the externalities. It becomes just one more way of socializing the risk of shareholders at the expense of labor.