A couple of years ago Gatwick identified that it had a (relatively) high number of both unauthorised and incorrect push backs. In order to try to tackle this a two part trial came in where ATC would give the push back direction in every clearance (dealing with incorrect pushes) and tug drivers would be required to be in the tug to hear it (dealing with unauthorised pushes).
When the trial results came back it was apparent that although the instances of incorrect push backs were largely unchanged there was a significant drop in unauthorised pushes. Therefore the requirement to be in the tug was made permanent. It has been suggested here that "the person trusted to fly the thing should be trusted to hear and pass on the instruction" but the evidence tends to suggest that by doing it this way you get a significant improvement.
The incorrect push part is more tricky to challenge as Gatwick has a large number of stands for which the standard push back is runway dependant and a number of instances where ATC will vary the standard push to increase capacity. This is why you will often hear ATC giving a push back direction on certain key stands for a short period after a runway change. Again the statistics seem to suggest that having the push back crew in the tug to hear the clearance reduces the likelyhood of error creeping in to these "non-standard" pushes.
So rather than being a case of "health and safety gone mad" it is actually a tested remedy to an identified problem that has produced good results.