Think it would be highly unlikely that the power points in a basement parking area would be part of a lot’s power supply. That would involve more complex and expensive cabling, something the builder would be likely to avoid.
I’ve heard of cases where owners have run freezer cabinets in underground garages taking their power from OC supplies. Those appliances could easily cost in excess of $300 in electricity per annum, nice if you can get an unsuspecting strata plan to pay for it.
Easy enough to check it out, without the services of an electrician, if you turn off your unit’s main switch, and the power stays on in the car parking area, then you’re using either OC supply or that of someone else.