I think that the person to whom you replied is speaking of outdoor installations, while you are speaking of controlled (maybe datacenter) installations. I have outdoor fiber running aerially between buildings on my property, in a region with massive seasonal temperature changes. Multiple local FTTH and Coaxial ISPs also run fiber on shared utility poles (the same ones that the electrical grid maintains) and when I look at the poles I see communications lines all in the same general area, often mere centimeters apart, if that.