If you read down where the Q&A is, it appears that they have firm commitments with some large banks. That'll certainly get the ball rolling.
In any event, all the things you say, "best spreads, best execution, best clearing" will be had on the CME/Reuters platform. Why best/better spreads? Because a bank will in all probability make more from fees than off a spread. Think about it. Competition has alread brought spreads down to 1 to 1.5 pips. Banks aren't making as much as they used to in the three pip days. And since the FX markspace will be avaliable to retail clients (Int Bkrs is committed to being one of the first to offer it), buckteshops don't stand chance unless they too evolve towards straight through processing with a fee(commission). I see Spreads going down to .5 to 1 with commission being the norm.
Currently with FX futures, EURO FX specifically, you pay 1 pip plus avg $6 RT fee. That translates into 1.5 pips. Avg bucketshop is charging 3 pips on majors, more sometimes if not fixed. Oanda happens to be one of the few who avg 1.5p on Eur/USD. Banks could do better, but don't currently for a number of reasons. But they could get it down to 0 to .5. That is if they can be compensated by charging a fee. If transparency increases, cross currency risk decreases(due to centralized clearing), and volume increases, fee based trading would probably become the norm. And that's what FX Marketspace is all about.
It has a very high probability of succeeding.