Yes, as were Karen Corr and Kelly Fisher. Seems like the women made the transition easier than the men...O'Sullivan gave it up, but Gray, Davis and Drago stuck it out with tolerable results...I'm pretty sure the current crop of Mosconi Cup Brits started out with snooker, too, but spent quite a bit of time playing British 8 Ball and the like before getting to the top of American pool.
As for ash, there's quite a few top snooker players using maple shafts, too. Ash is a nice solid hitting choice (hey, that's what the best baseball bats are made from), has a lot of the same qualities as maple in terms of wood "memory" and flexibility, but a little stiffer. But availability is the most likely reason it took off in snooker. Billiards and pool cues have always favored maple. I used to play decent snooker with my pool cues, the thinner shafts doing better but I had to focus on taking A LOT off the stroke to keep control and make shots reliably. But at the end of the day, I do better with a snooker cue than a pool cue. The smaller balls actually are easier to hit more accurately IMHO, so cuts aren't a problem...making balls that are close to a rail are a headache, though.
Ash would make a nice cue, IMHO, but I think you'd need to keep the shaft pretty skinny, I think. I've been thinking about having somebody make me a snooker shaft out of ash for my Carolina...brass ferrule and all. I'd get good use out of it here in Europe, but once I get back to the States it might not see much daylight...