It can happen. Usually when 2 factions are in an All out brawl with a good farm going and the 1 faction that is being ignored is very focused on capping something. But normally no. There is no reason the other 2 teams can't just dump 66% population to block them
Yeah, on waterson the vs even with drastically lower pop would win alerts sometimes. In some rare occasions mattherson NC would do very good too. One thing that always happens is that opposing factions pop drops once one starts to win. It's not all 4th factioning, a lot of people just don't like getting farmed, or they can't take a loss, and so they log off.