Private companies should never have the capacity to shut down substantial parts of a national economy unilaterally. If they do, it is a failure of governance.
The solution is not forced arbitration or back to work legislation - the solution is breaking up any company that has the ability use their market dominance to create this kind of economic disruption *before* they get the chance to hold the country hostage.
https://www.cbc.ca/news/politics/cn-railway-cpkc-lockout-job-action-negotiations-1.7301419