With 25 ft S mode reporting the pop-up RAs are pretty much impossible.
in effect an RA can only happen when both crews and ATC have not done their job correctly.
If they’re all jet aircraft that is and I’m assuming that as everyone has TCAS.
If we fly 10 mile legs we could have somebody diving through our altitude with (at best) 10 miles separation horizontally and worst case we’ll never know.
In that sense the question is a little academic.
The original discussion arose from an opposite premise, in connection with an incident where onboard equipment failure in one aircraft triggered RAs in several others. I was told it occurred at EDDM some 10-12 years ago, but I couldn't find any reports.