PIC can be in either seat in Oz as long as the flight manual doesn't specify a requirement for a particular seat. Some examples off the top of my head:
Instructors are nearly always PIC when teaching but are usually in the R. seat. Sometimes they're in the L. seat too but it's still usually PIC.
A Victa Airtourer's flight manual specifies the left seat must be occupied when flown by a single pilot.