It's likely that every tower is not a uniquely designed one off, so whatever external forces were considered were probably for the peak loads x peak degradation

It's likely that every tower is not a uniquely designed one off, so whatever external forces were considered were probably for the peak loads x peak degradation in some set of towers. I'd guess there are probably some areas where the towers are overbuilt by a useful margin. How good are the records and field measurements to get that evaluated would have to be considered.