I suspect this ploy is to enable CMC to attempt to enter the US market. At the moment CFD's and spreadbetting are unlawful in the US, and so there is a huge un-tapped potential clientele over there that they just can't keep their hands off. How they will pay for it will clearly be in wider spreads or by simply spread trading themselves, or perhaps they'll have some sort of offset price offering that moves within a larger band than the true futures market, just as they do with their indices products currently.
With the deals available through genuine direct access brokers such as IB you would really wonder who would be tempted to trade futures with a bookie?
I would imagine that it is this type of "punter" that CMC would love to get their hands on!
Cheers
Quercus