Imagine this...
It's 2014 and SARU are discussing their long term future, one where they see the riches of Europe eclipsing the competitive benefit of playing in Super Rugby.. They ask themselves, how do we approach this, how do we join Europe Rugby.
One person at SARU proposes they push for an expansion of the Super Rugby tournament, get SANZAAR to fund the expansion. If the expansion works then great, but if it doesn't then SARU could volunteer to take a hit and cut one of their teams, but instead of cutting that team they offer it to the Pro12, they use it to test the water and see if the broadcasters and fans like the concept.
In 2019 when the current SANZAAR broadcast deal is up, if the Pro12 concept hasn't worked then no harm done, they still look like a good guy to their SANZAAR partners because they volunteered to cut one of their teams. But if it has worked, if the ratings and crowds support the concept, then they now have a tangible and quantifiable grounds to negotiate with European Unions and broadcasters on to join those leagues. Alternatively, the threat to leave SANZAAR and the persuasion this holds allows them even more control of the SANZAAR model. Australia meanwhile, now offers less content to the model, thus gets offered a lesser proportion of the overall broadcast deal.