I did a strange test, I had a dvd I had burned with Imgburn earlier, I had imgburn read the disk and start writting an iso, after it got started I opened my computer and clicked on the drive and disk, which starts power dvd, it started playing after a small lag and imgburn was reading away, I cancelled both since it was only a test. Only possible scenario and a crazy one at that.
During a burn the drive would be locked, or let's hope so.