One thing to remember is that there are 59 districts and a whole bunch of splinter units that you can proberly find a spot or location that will fit your needs if you can get in there(easiler said than done sometimes).
For Sanitation workers it means talking to people and visiting locations to check their seniority.
For Supervisors and Supers it means going to Union Hall and checking the transfer book and board located there(last time I checked).
Note: Don’t forget if you have a transfer in, you might get your transfer request accepted at the worst of times, it is your responsibility to keep updated on this, that would make for a chance of really screwing you up if you changed your mind because things improved at current location.
Safety First – Safety Always – Stay Safe