I'm in a center with 13 routes and a driver sort and load. Start times vary by three hours depending upon your duties on the sort and load and whether you have a town route or extended (rural) route.
We have the language about posting on Friday for the next week. They adjust as needed and claim it as an "Act of God" which is allowed in the contract.
I'm the bottom (17/17) seniority full-time driver. My start time generally says "Call at 10:00" across the board most weeks. If I'm not scheduled to work that day, I sit around and wait for a phone call that comes anytime between 8:00 and 12:00 (I've gotten the call as late as 13:00) if it comes at all. If I am covering a sick, I get the call as soon as the sick driver calls in. If I am running a dump route, then I get the call between 10:00 and 12:00. It just gets frustrating after a couple of weeks with fewer days worked than weeks that have passed and you are sitting around every day waiting for a phone call.
This week (posted last Friday) was "Call at 10:00" except for Wednesday which was 8:30 start.
Monday - They called me in around 9ish for a 10:45 start.
Tuesday - No call.
Wednesday- Scheduled start.
Thursday - I knew Wednesday night from a fellow driver, not through my supervisor as he was at home by the time I returned to the building and didn't bother calling me, that they needed me in at 9:00 on Thursday to cover for the driver that asked me if I would cover his route.
Friday (Today) - No call.
It wasn't always this hokie. We used to schedule all the drivers (unless there were no vacations or drivers out injured/DUI) and offer from top down for drivers to volunteer to go home after the driver sort and load. I never got forced off the clock due to lack of volunteers.