Yes Dick, you are correct - it relates to 'lights-out' training in MOAs.
What it signifies is that under the US system, people who are stupid enough are allowed to enter an area where high-speed military aircraft are operating without lights, making them effectively invisible to non-participating traffic.
I suggest that it must happen often enough to warrant the requirement for surveillance. On one of US AOPA's training programs there's actually video of an AWACS aircraft providing that surveillance, presumably because the ground-based variety isn't available for that particular MOA.
Given the paucity of radar coverage in this country, it begs the question as to what numbers a cost/benefit study would spit out if we had to adopt the same procedures here. I've got no idea how much an AWACS costs to operate, but I bet it ain't cheap.