Is there a way for say, a 911 Operator to mark down an accident with road closure without being in the area? It could reduce the amount of traffic at the scene, increasing safety for responders and reducing hassle for area motorists.
Not at this moment…
But from my experience, Waze is continuously improving its features… so I will not be surprise if in a near future we are able to do road closures without being in place…
On the other hand, Waze is also cooperating with authorities in some crisis situations… so, maybe also in a future could be cooperation possibilities with emergency services…
At the end, it would be good for all. 
This would also help prevent people from reporting while driving. We’ve all driven alone before…Being able to post from a different position than the actual scene would give us an opportunity to pull into a safe area and post for our fellow Wazers!! 