I'm the moodle admin at the same college as Brett. I just wanted to confirm what he is saying and respond to your question.
I've tested it on a fresh download of 2.2 stable, as well as qa.moodle.net and experience the same thing. The student can only see the final grade, any comments and a response file (if available), but no access to rubric definition or the actual grades of each criterion/level.
See attached screenshots of our local site, as well as qa.moodle.net.
Perhaps it wasn't part of the original spec? Or a bug? Or a permission that needs to be flicked on?
In any case, thanks for your help (as always)!