Many ops are certified to run different rides. I suspect that the longer you work at a park, that the more rides you will end up being certified to operate.
A friend of mine has worked at SFGAm for years, and I have seen him on Raging Bull, Giant Drop, Demon, and a few other rides (I want to say I've seen him on all the rides you mentioned, but I am not sure). Maybe it was him that you saw (his name is Kevin) ?
*** This post was edited by Joe Carroll on 6/19/2001. ***