Yes, it is possible that Metro can have all of its elevators working at the same time. Take a look:
I saw this at Glenmont on the way into DC on Saturday for an Anon raid. I know – I’m as surprised as you are. But Metro actually did get all 200-some elevators working at the same time for once. This just amazes me.
It’s kind of like when Metro actually has all three escalators at Dupont Circle’s south entrance working at the same time. I am similarly amazed whenever I see that. That happens about once a month or so, and yesterday was it. Otherwise, it’s fairly common to see one or two escalators down for repairs, with one running up, one gated, and one as a walker.