if it's truly OEM (factory installed and on the option label) it'll be powered by the AMP in front trunk. If it's just OEM then it could be either.
Quick ways to check:
- make sure AMP is 6x40W (unbolt from firewall or use a mirror to read label facing firewall). If 4x40W then no. If 6x40 then make sure pins 5, 6, 15, & 16 in the larger plug of the AMP are filled.
- pull the h/u and make sure there is not a brown plug into socket B (it would be brown IIRC)