The Strata is responsible for the wiring in the common areas but in apartments a lot of the walls are common property and so any wiring in these are Strata responsibility. Any wiring within the lot (not in a common wall) and servicing only that lot is lot owners responsibility.
In NSW it’s a nightmare.
Download a copy of these
2011_07_Defining_who_is_responsible_for_items_in_a_Strata_Scheme.pdf
2011_08_Identifying_common_property_in_a_existing_strata_scheme_2.pdf
which should help you through the nightmare.