I would be interested to know where the defamation took place. Anything said in the Senate Inquiry is subject to parliamentary privilege and the ATSB report can't be used as evidence in a court of law. That only leaves media outlets and I don't recall anything defamatory being said on ACA or TT!
If Mr Entsch is serious about exposing corrupt practices then he should be calling for a Royal Commission-something that has a bit more clout to it.