/usr/share/unity8-desktop-session/sensors.txt is in unity8-desktop-session-mir 1.0.12+15.10.20150609-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | create proximity
create accel 0.5 1000 0.1
create light 0 10 0.5
|