Crikey. If they need a crane to put up a new mast then I do wonder how the mast could get so damaged as only a really strong explosion or direct hit from a heavy vehicle could normally damage a heavy duty steel lattice mast like that Orange mast. That mast is basically the 15m high bottom half of what could be extended to a 25m mast as the base is built so strong in the first place.
Alternatively, if you meant a cherry picker, then someone is going up the mast to fix or swap the antennas / feeder cables.
I have a sneaky suspicion that all they might be doing is adding an extension to the top to raise the height of the mast. This will allow another array or two of antennas from another network to share the mast. Normally, Orange would move its arrays up to the top and allow the sharer below. But, in high locations like that there is nothing achieved from raising the arrays and only an interuption in service for a few days.