After a tiny bit of experimentation with Leopard launchd jobs that have multiple triggers, I found that they can in fact run as expected when either trigger is hit.
I had a working launchd job that used the StartCalendarInterval key. I then added a WatchPath key and rebooted for good measure. When I used `touch` to modify the watched path, the job executed.
Good to know, even though I’d never tried this in Tiger. I don’t yet know if there is a limitation on how many triggers can be added successfully, or if there are triggers which cannot be combined.
One immediate benefit of this, however, is that you can have one job that will definitely be coalesced into a single execution whenever it is missed (as with system sleep). If they don’t coalesce into a single execution, it sounds as if the developers at Apple would consider that a bug. Multiple individual jobs do not coalesce if they are defined in separate plists, even if they call the same script or command line tool.