You should be able to do this with a related list condition in a report (you can then use the resultant query in a script):
Encoded query for any incidents with an outage:
RLQUERYtask_outage.task,>=1,m2m^ENDRLQUERY
You can change the greater than or equal to 1 condition to "none".
Encoded query:
active=true^RLQUERYtask_outage.task,=00,m2m^ENDRLQUERY
While you're making your report you have to click on "related list conditions" to expand it, once expanded you can can choose the table (outages) and change matched records to none. You won't need a filter because you are looking for anything unrelated to any outages.
Does that make sense?
