Mountain Lion was released in July 2012, its encryption code was effectively identical to that in Lion. As is usual Apple still had to apply for a new certification for Mountain Lion and did so. However the wheels obviously grind very slowly and it was only on June 14th 2013 that Mountain Lion finally received FIPS 140-2 certification.
This should now make it possible to use Apple's built-in FileVault2 encryption in organisations that require a FIPS 140-2 certified product. I myself have been using PGP instead due to this issue.
Anyone interested in doing this should visit the following two links
http://csrc.nist.gov/groups/STM/cmvp/documents/140-1/1401val2013.htm (search for Apple)