Learner drivers on the motorway

Learner drivers are not allowed on the Motorway. We all seem to believe that this is only barely enforced and maybe that's true. I see many L signs when I'm on the M11 or M50.

Still, I was kind of surprised to see that at Carrickmines all traffic is being diverted onto the Motorway due to road works.

The road to Cornelscourt is closed (due to Luas works?) and there are orange diversion signs indicating that traffic should use take the M50 to the next exit (Louglinstown/Dun Laoghaire). That means any learner driver who comes across the motorway there to get to Cornelscourt is being directed onto the Motorway. Is this legal? Just curious.