In the thread of Argentinean MVNO* there is a really interesting explanations about the model of cooperative, and another example in UK. I'm not against the strategy of joining forces to compete, but in my humble opinion this are signs of a different phenomena.
What I can see are the early signs of unionization against the biggest, but not recognized as MVNOs - Google, Apple and akins. Multi-brand combination as cooperative or consortium, whatever, this mean joining forces to compete and survive in a change context produced by the internet. Economy of scale or charing risks smells a sign that those companies are too committed with a service coupled with the technology they bought, or represent. Then, Someone must have said: Let's fight together. So, an MVNO looked to be an common sense among them. Is this a real rational choice? I doubt.
Again, in my humble opinion the telecom operators should dress itself as carrier, and gain real economy of scale. In the social networks, or any real life networks, the laws that governs it are growth and preferential attachment. Means that to capture the preference you have to be big and popular - translating it to telecom and IP networks means produce links with the subscribers as much as possible. The real competitive arena resides on knowledge about Social Networks "choices". In this sense be real is more important than be virtual.
Really, virtual organizations as cooperative or consortium does not mean that they will really agree on every decision taken, simply because to reduce costs someone should be cut off (cost reduction). Control important areas means power and means fight for that power. Who will survive in their internal network? The market will wait for?
Fusion is the appropriate model for this competition, because in the internet arena the rich gets richer. In the current scenario I'm afraid that MVNO is a big mistake.