What service is used to serve the same ad in multiple locations on a single page load?
It appears in this example Google is serving the ads, however I don't see an option for this in Google Adsense.
It sometimes happens in AdSense by chance, but the publisher cannot control it. Well ordinary AdSense publishers cannot - I don't know if it's possible for the premium account folks, who have a lot more options.
And sorry, but I don't know any services that offer multiple ad-units from the same campaign per page.