Are you asking if PACU nurses are required to float to other units when needed and there isn't sufficient need for them to stay in recovery?
If that's the question - then "yes"- at smaller facilites. At larger hospitals, then the answer is "no" - they always have to have their PACU staffed and those PACU nurses generally put their foot down about working elsewhere.
I have worked at both; now I work at a smaller facility where we have indeed been told to go "help the floors or the ICU" when there are no surgeries scheduled. The beauty of it is that our PACU nurses work ten shifts and the rest of the hospital works 12 hour shifts. So we are never asked to "take patient assignments", we usually just go out and help the nurses with admissions and discharges, restarting IVs, etc. If we aren't busy in PACU or preop (which isn't very often) then two of us usually work as a team and go from floor to floor and help where needed. It isn't a 'requirement' per se, but a request from nurse mangers. I know that many PACU nurses balk at this, and I know many will say my attitude is beyond absurd - but I really don't mind helping out. Here's why: I would rather stay busy and make the day go by faster.... I am not one to enjoy sitting and waiting for nothing to be coming out of the OR.... I enjoy going to the ICU to 'keep my skills up'.... I enjoy the appreciation the overworked, busy floor nurses give us when we help their day go a little easier.... the alternative is being sent home because there is no work for us .
Since we don't have to take patient assignment, then if a case comes up, we are available to go back to PACU when necessary. If your place is trying to get PACU nurses to float to other departments and take assignments, then they will be in trouble when the OR adds cases and noone will be in PA to recover!!!
I work in a Phoenix area hospital, and we do not float our PACU staff. It is never a concern (thankfully) for us. We sometimes have qualified resource staff come to us, but we never go anywhere else. The only thing that would be close, is when a PACU nurse goes to ICU to help recover a patient because the ICU nurses feel overwhelmed when a patient goes "direct", and demands help.