Well, if you select a weeks vacation it's not available for another driver to choose. Then you work said vacation. Cover driver is unable to take vacation and is unable to work also. As far as paying you twice, it's a wash. If you take it you get a weeks vacation pay plus cover driver gets his pay. 2 checks. If you work you get a vacation check plus your regular check, cover gets nothing. 2 checks.
Here vacation coverage jobs are bid jobs(regular full time drivers). On thursday of the preceding week a list goes up with vacations available to cover. You sign in seniority order what you want to cover. If no vacations, or if you don't sign list, you come in and are assigned to whatever route is available. So if you work a bid vacation you are actually taking the work a cover driver is entitled to.
Here, "they" don't even know who gave whom off. Every AM, they post a list of which cover driver is running which trip and who is extra. Then several things happen.
8:15, Cover driver A comes in and see's that he wants to run a trip that a less seniority driver is on. Several moves are made to accommodate driver A. This, could easily move 3-4 drivers.
8:20, Senior bid driver comes in and see's there are extras and he wants to go home. Several moves are made to accommodate senior driver.
8:25, Someone had called out but someone dropped the ball, so several moves are made to accommodate the call out.
8:30, Someone notices a trip is sitting and so several moves are made to accommodate the sitting trip
8:35, On a rare occasion, get message on DIAD "to meet another driver to swap trips as he doesn't know the trip he is on.
I have been moved 5 times in the AM.