I do a bit of that work myself,... on a much smaller scale, a lot closer to the ground.
Lads,.. on the helmet issue,.. it might seem a bit silly wearing a helmet up there, but a helmet will save you if you are caught by a gust of wind loose you balance, and get thrown against the building head first, which can happen very easily when you're swinging on the end of 100' of rope!
Also, their gear should be secured by a light rope to their harness,.. for the safety of pedestrians walking below.
And,.. it could just be me, but I can only see 1 rope? I can see a reflection on the glass which looks like a second rope at a glance. NEVER EVER attempt this kind of work without an active safety rope!!
It's great money if you can get the work though!