One of my engineering projects that I did years ago was on a tower with support lines. Engineered properly and for the locations, the towers will be fine. Now, if what they said about antenna size and weight is absolutely true, then tower redesigns would HAVE to be done.
Every area has different climates that have different environmental phenomena that occur. Ca. for example has earthquakes and high winds, which are coded for in the civil engineering designs for the city/county. The towers, if an engineer designed them right, should withstand a max effort from most environmental situations. The one that fails, atleast here in Ca. will have one heck of a suit on their hands, especially if someone gets hurt.
I could see them building deidcated towers for a new setup if that is required for the size of the equipment.