I doubt it.

Environments that cold need really well insulated spaces, and a lot of Melbourne homes are really poorly insulated. The apartment has one advantage, in that it would be small and therefore relatively easy to heat through even improvised means, but holding on to that heat for any length of time would be difficult

Maybe with a group of people huddled together in a blanket fort? I’ve never experienced temperatures like that myself but I remember a whole lot of advice going around during last year (?) power blackouts over winter in the US. People camping in their living room and staying in the one room to concentrate heat sources. That said, I don’t think it went down to -20 C though. Wouldn’t water pipes freeze and stuff as well? I suspect maybe it won’t be survivable. 🤔