Note that the DBCDE’s FAQ suggests that for high trafficked sites they will request the takedown of RC material per site policies. I would assume that if a high traffic sitel did not have such a policy it would be blocked.

User-generated content provides the greatest
challenge as where prepublication moderation is not possible, such as in Facebook, it is highly open to competitive sabotage. In particular, with a secret black list, any moderation is ineffective if the moderators are unaware of which site links are blocked.

These issues apply to government as well – DBCDE itself published a blocked link submitted by a user during their Digital Economy consultation last year (it remained accessible for several weeks before the user post was disappeared). As far as I know the Department was not fined.

Also critical to note is that the discussion of illegal content would also be an offense, like the wikileaks example you gave. Therefore any material discussing how to circumvent the filter or how to counter those methods would be blocked, making intelligent discussion on improving the filter impossible online.