Afaik the bill only forces the workers unions to accept the deal, which they can accept and then strike the new deal? Or just plain refuse in a “they can't fire all of us” way?
The fact the government didn't even get them sick days was a disgusting failure and lack of human respect for these workers. They obviously know how important the rail workers are for the economy, but they need to be shown they can't just force the problem to go away. The most disruptive time of the year for this to happen too.