With all this war rhetoric thrown around, it seems a reasonable jump to declare essential workers troops on the frontline deserving of what we give other troops (free health care, pension, heavily subsidized secondary education)
I don't think you should be looking for legal precedent, just practical one.
Depending on the severity of the impact, governments would (and did several times):
1 - Declare the strike illegal and order people back to work, fine and at the worst case arrest the organizers if they don't comply.
2 - Declare the involved unions illegal, free companies to hire whoever they want and disobey agreements.
3 - Conscript people into doing the work, either by using the company as middle-men or by literally enrolling them on the military and absorbing the work.
But I don't think any government will have to do any of that. A strike does not fit this crisis very well, no party would gain anything.