witwiw, silly question, i'm sure you've already thought about this. But as you can see it through some Binos have you been able to see the Rego at all? or maybe any distinguishing markings or logos or anything like that?
Quick search of the Registry for 208s with their Registered Operators State being VIC shows only 2:
OPH - NAUTILUS AVIATION PTY. LTD.
UCR - U C AVIATION PTY LTD