On twr, we didn't get any information about problems until they were on approach, so it's pretty obvious they expected the altn systems to work normally. And only then did the problem arise. After that they circled for 90 mins, in contact with hq and one instructor pilot, so I assume all possibilities were checked, though of course we're only humans.
On our request, police closed the road just outside the airport perimeter. And then just waiting for the outcome, and lots of smell afterwards.