Apparently, the dudes have a ladder long enough to get up to the upper level, but the balloons are tied to to the rooftop, so they appear to be safe--for the minute.
This piece would have been much safer, and stronger, if Banksy had actually painted the graffiti onto the building. Have never seen one cut out of a building this high up. Just sayin'.
Ironically enough, some of the folks on the scene are calling the cops to protect Banksy's vandalism. What a strange world we live in, and as Banksy says in his audio, why live in a world decorated by art, when we could live in a world made of art? Watching how the public fumbles over how to deal with a Banksy, its real life art (chasing after art).