A quick Google search shows a press citation:
“I saw old mate fighting, we crossed the road ... next thing (Mr Mill) was on the ground.” (Sunshine Coast Daily, 25-06-2008)
and more interestingly, most of the Google hits seem to show sites from Queensland. My question is: speakers of Australian English, do you recognise the phrase "old mate" used in this way, do you use it yourself, and which state are you from? Is this a Queensland regionalism? And speakers of other English varieties: have you ever heard "old mate" used in your English?