We got paid according to how 'flexible' we were at my last facility. There was a graduated pay scale according to whether you were unit based prn (lowest prn scale)
or agreed to float to 4 areas (highest). Some facilities have graded payscales that take into account how many weekends and holidays the prns/floats will work too.
My float pool was critical care and we had our own dept director over the float pool.
Every place does it a little different in my area...but not too much different than other facilities or the nurses move on to greener pastures. Thats a perk to being in a bigger marketplace.