I think it may be a case by case scenario but most are simply shutting down for a few weeks.
I know of some shows that were in rehearsals and those just shut down. But then, CSC's Assassins hasn't announced what they're doing yet about their April 2 start, but I bet they shut down and push back even 2 weeks.
As for subways, remember NYC isn't on lockdown. People are still working and expected to travel; the subways are running. Events larger than 500 people were banned and under cut in half. That's not a lockdown.