We still had an embassy in Iran when the Liberals under Chretien failed to secure the release of the Canadian Zahra Kazemi, who was killed after being raped and tortured.

You admit in your own comment that there is a low probability of success even with diplomatic ties.

Yet Iranian-Canadian citizen Hoodfar was released without benefit of diplomatic ties.

Therefore: Diplomatic ties are irrelevant and you are just trying to deflect blame onto the Conservatives instead of taking responsibility for Liberal shortcomings.