Mario,

I can't really speak for all industries, or even too many people, so I'll just speak for myself, a contractor doing work for various clients, but notably not in the nuclear sector.

Aside from the modules built into CAESAR, I've only seen requirements to use API 6AF (which is limited to API flanges, of course); I personally haven't seen anyone push WRC 538.

I can't really comment on the familiarity of one committee's members' on another committee's works. I would speculate some of the same reticence will remain, even within the same umbrella Society.