I might have missed some of the points here but I've just tested here (albeit with one caveat; I was doing it WITH a user logged on to the PC; however, I was NOT seeing the calibre icon on MY system tray).
I scheduled a news download in calibre for 10:30 PM.
I stopped calibre.
I created TWO tasks
Code:
Name: Test-Calibre
When running the task use the following user account: Peter-W7\Peter
Run whether user is logged on or not
Triggers: Daily @ 10:15 pm
Actions:
Start a program "C:\Program Files\Calibre2\calibre.exe"
Arguments: --start-in-tray
Settings:
Allow task to be run on demand
If the task is already running then Do not start a new instance
and on saving the task supplied MY Windows password
Code:
Name: Test-Stop-Calibre
When running the task use the following user account: Peter-W7\Peter
Run whether user is logged on or not
Triggers: Daily @ 10:30 pm
Actions:
Start a program "C:\Program Files\Calibre2\calibre.exe"
Arguments:--shutdown-running-calibre
Settings:
Allow task to be run on demand
If the task is already running then Do not start a new instance
and on saving the task supplied MY Windows password
Monitoring via pslist -t initially I see a calibre process running under a taskeng, then a calibre-parallel under the calibre.
Monitoring my calibredb directory I see a new book being added under the calibre author; for a period of time after the download completes both calibre and calibre-parallel are still present.
Eventually a second instance of calibre starts (the second job) and then both instances of calibre terminate.