Australian Capital Territory Consolidated Acts(1) In a proceeding in the court, the defendant is entitled to relief (whether at law or in equity)—
(a) against the plaintiff, if the relief claimed would have been granted to the defendant if the defendant had started a separate proceeding against the plaintiff; or
(b) against someone other than the plaintiff, if—
(i) the relief claimed relates to the subject matter of the proceeding; and
(ii) the person is served with written notice of the claim; and
(iii) the claim would have been granted to the defendant if the defendant had started a separate proceeding against the person.
(2) If a person is served with a notice mentioned in subsection (1) (b) (ii), the person is taken to be a party to the relevant proceeding with the same rights as if the defendant had started a separate proceeding against the person.