Your 600 driver hub can accommodate an on call board or a qualified board to cover absences, injuries and vacations.
Smaller centers cannot. No one would stay on it. They would not be working enough.
Yes, at least in the Central.
Wrong.
The Central says that there must be at least 10% of the feeder jobs on the qualified list. Some of the hubs have an on call board. Some of the smaller centers have feeder qualified package drivers to fill that 10%
These drivers are package car driver on the feeder qualified list that usually deliver packages. Sometimes they are used to cover feeder vacations, injuries, or other shortages. Or even extra peak jobs. For most of the centers, they are not used to cover a 1 day call in by a feeder driver. The closest hub usually covers the job.