So the answer is when loc is alive, (one dot, alright), not when VOR/LOC turns green on the FMA right? (we are on the B737 here).
I was told that the VOR/LOC mode is more accurate than the actual localizer deviation indication and scale. Some pilot of my company will assume that we are established on the localizer (when on auto pilot) when VOR/LOC turns green on the FMA. And not before.