Today I was on Phase 4 of one of the combat missions in P1 of Geo TB. I opened the round by using Traya's isolate on the Arc Trooper so he didn't spread his brick wall buff (can't remember what it's called). However, once the Arc Trooper's turn came up, sure enough he spread the locked buff to the Sharpshooter.
Screen shot below, and yes - he was isolated before the buff was spread for those that may be wondering.
Has anyone else run into this? I could be missing something about the buff being unable to be prevented or something but I was under the impression that Isolate blocked that...