it would make sense on some level but if they do have sleeper agents how deep are they in the real world and under what circumstances would they be activated?
Does the Foundation have moles in other occult GOIs? Probably. Are some of them occasionally awaiting activation, or unable to communicate with handlers? Sure.
They probably have sleeper agents of varying levels, from "basically just a mole" to "doesn't even know he's a sleeper". With the Foundation's knowledge of mind-manipulative stuff (memes, cognitohazards, etc.), they could probably bury a sleeper agent quite deep inside another organization. As for when they'd activate, it would probably be highly dependent on the situation.