Yes, everything at CERN, at least in the 2000s, was in AFS. Fermilab was also using AFS extensively.
I remember compiling AFS from source for Scientific Linux 3.x because there was a weird bug that didn't let the machines mount AFS when they were integrated with LCG (before it was renamed to WLCG: https://wlcg.web.cern.ch/)
Oh my... this comment really dates me...