An Exadata simulator VM environment exists, but it's restricted to Oracle internal use. Martin Bach wrote up a good summary of some of the issues involved at http://martincarstenbach.wordpress.com/2011/12/08/the-cause-for-and-against-the-exadata-simulator/
It is unlikely that Oracle will release this as it is a competitive advantage and the simulator would have Oracles proprietary code hence releasing it freely might have legal implications. Even till date you cannot legally posses Exadata manuals unless you own an Exadata machine as the documentation is part of the proprietary cell server storage software. Making the simulator available would lift that restriction. I do not think this would be made available to anyone outside of oracle and perhaps in the future a few select partners.