iTunes Match went partially live internationally in several markets on December 15, with iTunes accounts in New Zealand, Australia, the UK, Canada, and other countries offering iTunes Match signups in users' account preferences. However, that launch appeared to be premature, since iTunes Match wasn't advertised on the main page of those countries' iTunes Stores and signing up for iTunes Match didn't actually do anything.
Apple began offering refunds to customers who signed up for the service after its premature launch, but only hours later the service has indeed gone live, with links appearing on the main page of the iTunes Stores in countries where the service has launched. The above screenshot is from the New Zealand iTunes Store, and clicking on the iTunes Match link immediately offers the expected signup option.
International users are reporting that iTunes Match is now operating as expected, so after 18 hours or so of confusion the international launch does indeed appear to be underway. Apple has not yet updated its international sites to include information on iTunes Match as of this writing, but unlike yesterday international users are successfully using the service after signing up for it.