First up, it doesn't look like there is a single disc version. If there is, it would have to be under $20. And if there isn't one in the first release of the TF2 DVDs, it may be out later.

I had emailed Paramount Australia for details on what we are getting released in Australia, but they are useless when it comes to relying on them for emails, so once again I never got a reply.

They are better with phonecalls though, and I did at least ask for info on the IMAX version (exclusive to US Walmart). According to Paramount AUS, there are no plans at this stage for it to be released here, and they can't say if it will eventually be released here (like next year - because often special editions like that can make their way here eventually).
So if you want the IMAX version, it might be best to import it, in case we never get it here (provided there aren't compatibility issues with US Bluray to AU players and TVs).

TF2 2-disc DVD - $20-25
TF2 Bumblebee pack - $45-50
Bluray TF2 2-disc DVD - $40-45

TF1 - $15-20 (released about a year ago)
TF1 & TF2 Double pack - $40-50
Bluray TF1 & TF2 Double pack - $70-80

For details on the contents of the TF2 DVDs, check this link.