Photos of scratches can be a bit misleading but I admit that this one does look like it could be the real thing. I will send the link to Jaimie Hopkins in Office of Nature Conservation. She detected Gula (koalas) in a survey across the ACT recently, using sound recorders. And also to Chris Malam, also in ONC, in case he wants to fly a thermal drone down there.
Ok not koala bites, so that leaves only the scratches. Usual suspects are Lace Monitor (rare in ACT), BTP (common in urban area), RTP? and Gula. And I omitted to say before, well done Nina for spotting these and recording them.