I just tried a bunch of cogs (SunTour, Dura-Ace, Euro-Asia, etc.) on a Campagnolo Record road hub and the only two that offered more than a thread or so of engagement for a lockring were both long out of production: an early 1950s Sturmey-Archer cog from before they adopted the splined cogs, and another marked "Reich."

N.B. if you're going to run a fixed gear on a road hub, lockring or not, keep the rear brake and don't use your legs for slowing down or stopping.