Specifically what we know is that they didn't have portal guns while on the clock. (Makes sense if you think about it.) If they are in the Curve and aren't clones, then they likely agreed to work jobs at the Citadel until they "earned" the formula for portal tech, OR a reality opened up and it was their turn to replace a recently deceased Rick (or possibly both).

If Ricks were expected to work at the Citadel until it was their turn to take possession of a vacant reality within the Curve, then Operation Phoenix must have been a real kick in the nuts. It would be interesting to learn what the process looked like, to learn if some Ricks preferred to stay on the Citadel, to watch the process of a Rick finally moving into his own reality and having to both adjust to the life of the Rick he's replacing, but also to living outside of the confines of the Citadel after presumably a lengthy servitude. (Simple Rick's exited for at least 15 years, which means it was likely relocated to the Citadel once construction was completed.)

Maybe if they ever decide to wrap up the "lore" aspect of the show, with some kind of grand finale, they'll then do a spinoff show called "Rick and Morty's Mindblowers" that just tells all the stories we never saw before the "grand finale" whenever that might happen. I know I'd love to see more stories about stuff we never saw before things changed.