I don't think you would be permanently laid off. What about those with less seniority than you? I think you could displace the least seniority part-timer. I could be wrong.
Not sure of your individual supplemental tie-ins, but ;
-you can only have 1/2 of your 8 hours changed per day.
-one hour shift in start time per week (up or down)
-the number of 22.3 jobs must be maintained at each center each bid time.
-The job itself can be changed (start time, days of week, job duties etc) at bid time, but the job must be replaced somewhere.