They also did something like this in the recent remake of "Robocop". Some thugs are in a diner having a discussion, and it's caught on CCTV. Later, the main character goes back and analyzes the video and extracts the audio from it, presumably based on some vibrations somewhere in the scene. They don't say, but I got the impression it was from the window vibrations, similar to the technique of shooting a laser at it and watching the vibrations of the reflected light.

lol that is the first thing that I thought as well. I just passed it off as a typical Hollywood trope, but now I'm quite delighted to see it become a reality.

The first thought to cross my mind.