Depends what they're doing there. When I was an apprentice with the MOD the radar opps used to cook seagulls in flight when the were bored.
I suppose you have to be in really close to do any serious damage but having seen some of what was at that time the BBC transmission departments black museum of RF damaged rigging, both direct and induced damage, including a melted section of an aluminium ladder which had been left out on the ground in the middle of a mast farm!
Also the riggers saying that even with the RF power turned down you'd have to climb past the transmitters rather briskly to avoid having your fillings melt.
I'd tend to err on the side of caution.