I think the quote is in the Bill Flanagan book, but I couldn't find it, so I googled and found this on a Spanish U2 forum:
"We were traveling the same routes as these girls, staying at the same hotels, though we weren´t walking in the same shoes. (laughs)
...There was a certain fascination with their power with the populace. It goes back to the silent movie stars. Because in the thirties, Hollywood was never as powerful as it was in the silent age, and there´s great power in not opening your mouth."
"And these super models (Christy, Naomi and company) were the silent movie stars of our age. Blank faces and stares that on one level suggest a kind of erotic acquiescence, and on the other a kind of spitting at the cameras, a kind of annoyance seasoned with mischief (laughs). There was something very powerful. When you got to meet those who were at the top of that particular tree, they turned out to be very clever, very smart manager of their own brand, in the case of Christy, Helena, Naomi and Kate, people you´d want to hang out with"