It's an interesting tfL map - the Met line for some reason is operating normally. I think the AB staff will be able to get in to work - it might have been easier for them in their previous office though.
The line's working but almost all Zone 1 stations are closed, including Barbican and Moorgate. You can't even open the door and leap out as the train passes through these days.
I'm sure they'll make every effort to get in - I would hope so. Not feeling very sympathetic towards the results department at the moment.