Thinks - why aren't the engineers trained and licenced to use radios?
It seems to be one of those things that the CAA seem to turn a blind eye to, until something goes wrong I guess.
When I was an RT examiner I did do a course and exams for a few engineers, TNT were one that got all their engineers licensed, as did Irvin Parachutes for their guys on the ground while they were testing at Henlow.