My boss considered the H&S side of it with regards to working at height and decided that rather than wearing hard hats we would just take sensible precautions to avoid accidents, after all the hard hat worn by the guy at the top could fall off and injure the guy at the bottom, so we just avoid being under anyone when they were working up a mast whenever possible, if you have to below them then the person at the top doesn't use any tools so they can't accidentally drop anything on you, and wherever possible the tools are on lanyards.
Basic common sense, after all whether I go up the mast or my mate does we are both responsible for the others safety, so the guy at the top tries not to drop anything on the guy at the bottom and the guy at the bottom is responsible for winching the other guy up and lowering him back down again in one piece.
That would be ok but hse have banned the use of man baskets on forlifts and telehandlers in anything but emergencies if the work is none emergency cpuld of been forseen or such like scaffolding or a cherrypicker must be used the only machines exempt are some of the new telehandlers that can control the machine from the basket