I don't know that the issue will be so much whether you can image them with Mountain Lion. You can probably make it work with the right boot image or Netboot set, but afterwards the reporting into Casper will be way off. Older versions of Casper Suite cannot properly report on Mountain Lion Macs, for example, the OS version shows up as I think 10.2 or something like that. It will make Smart Groups and searches report inaccurately. And there are other problems beyond that.
Short answer - I would not recommend it.
