Had that happen with a Citroen BX company car - discs all round & the handbrake acted through the caliper. Other rear disc brake cars I had before had seperate parking brake drums & were not affected by disc cooling. A good reason to leave the car in gear (or "Park" with an auto) and not just rely upon the handbrake.
I won't work on electrically actuated parking brakes - they need specialist knowledge that I don't have access to to work on them safely. I have heard tell of a mechanic replacing brake pads loosing fingers when the electric brake was accidently operated - don't know if it was true or just a "scare you off" doing your own maintenance tale.