To support concurrent work of editorial designers and advertisement staff on different layers of the same page, a typical solution is to assign a higher lock level to the advertisement staff than to the editorial staff.
Example
Assign the lock level 100 to advertisement staff, and the lock level 99 to the editorial designers.
This provides a protection of the advertisement layer against unlocking by editorial designers. Editorial designers cannot move or delete ads on the advertisement layer.
Note: such lock level distribution does not protect editorial layer against advertisement staff access, but it is assumed that ads are anyway placed automatically, thus that advertisement staff does not deal with pages directly.