No. When you change the language, it change the region to where it language is associated with. So you would not be able to use the Australian Siri voice and have it search in Canada.
Can I use Siri in any of these languages in other countries?
Yes. You can enable Siri in any country, and you can choose to speak to it in any of the languages that Siri supports. However, Siri is designed to recognize the specific accents and dialects of the supported countries listed above. Since every language has its own accents and dialects, the accuracy rate will be higher for native speakers. Find more information regarding which Siri features are supported around the world.
What an annoying new and impared addition to the iOS. I can't imagine any iPhone user would ever want search results that pertain to a place thousands of miles away, based on their accent. 7.0 Siri seemed to understand that just fine. Worst of all, there's no way to define Siri's default search parameters. What a pity.
Thanks again for the quick reply mate!