AFAIK, they're all heated when the ignition switch is in position 2. See the owner's manual p. 57.
Check Bentley's vol 2 p. ELE-667 connector X257. WS/RT and WS/BL wires connect the electochromic rearview mirror to the driver's side electorchromic side mirror.
2001 530i/5 S+P CDV delete/Akebono ceramic pads
M5 SSK/RedLine MTL/M5 rear sway bar/Bilstein HD
BMWCCA Member #337964