In our hub bidding of new combo jobs go to combo employees first. Then that combo job is bid to other combo employees. The 3rd bid goes out to high senior part-time. If no combo employee wants the first combo opening then part-time employees are first to bid to the job.
If a full-time job goes up for bid, full-time employees in that classification are first to bid. This happens twice. 3rd bid goes out to the general full-time employees. Full-time combo employees are only allowed to bid to that job after all classified full-time employees are allowed 1st and 2nd bid.
Just think of it this way. In our building one bid sheet goes up for every combo job. Everyone from combo to part-time can sign it. If a combo person signs the list he or she gets priority over all part-timers regardless of their seniority. If two or more combo workers sign it the combo worker with the most combo seniority will get the job. If no combo workers sign it or those that did turn the job down the highest senority part-timer gets the opportunity to take the job.
The same goes for fulltime inside jobs. For example we have fulltime feeder wash jobs in our building where someone will wash feeder trucks for a full eight hours. All employees who are considered "fulltime inside" get priority first, then combo workers, then part-timers. The only time I see it act differently is when there are open feeder jobs. They post a list for package car drivers first, then they post a list for only fulltimers and combo workers to sign. Then once in a blue moon they post a list for part-timers to sign if they don't get enough people from the first two lists.