Hey Hans,
Good question. WordPress has made it known that they would like any open source plugin in the WordPress.org repo to go through WordPress.org for the translations process. We like to play by WordPress standards any time we can, so this is part of that process.
So, in other words, those updates should show up when The Events Calendar is pushed and new translations are indeed available. On the other hand, the premium plugins are managed on our translations site, where they are always available to update — though we do roll in updated translations with each dot release.
Cheers!
Geoff