Free Rescue- Await Recovery. How do they know?

I drive back and forth between J16 and J17 of the M4 5 times a week and for several months now, they’re doing road works on about a 5 mile stretch. Across the 5 mile stretch there is a 50 mile an hour limit, all the motorway phones have been diabled and there are signs stating. “Free Rescue- Await recovery”. Given that
[ul]
[li]Sometimes there is nobody working on the road at all[/li][li]When there are people working on the road, they may be working a patch miles away[/li][li]There’s no phone number or other contact information[/li][li]There are no cameras along most of the stretch[/li][/ul]
How do they know you need rescue without you doing anything? Especially if you break down at 3AM on a Sunday morning.

How do you know this? Cameras can be small and put up quickly.

Well, the sign doesn’t say how long you’ll have to wait…