Hi Kath,
Sort of, yes, I think it’s doable.
While the search override may not trigger because of the custom page, you can definitely send the search to redirect to that page and let the other search do it’s thing.
To do that, go to the Search Behavior -> Magnifier and Return actions menu, and set the custom redirect URL to this:
jobs/?jq={phrase}
If all goes well, the plugin will redirect to the jobs search page, with the pre-populated search query.