It's hardly surprising he didn't a response to his letters to Mark Ratcliffe sent in December 2017 considering he left Chorus in February.
I'm actually slightly confused as to what the issue is here and what is stopping the driveway from being resealed. Shallow trenching has "shallow" in it for a reason and is a pretty normal method of running cable. From the picture though it's pretty hard to understand what the driveway looks like. If they're removing all the existing concrete for the driveway it'll simply leave the exposed cable which can simply be concreted over - it's not going to damage it.
I read it as the company contracted to replace the drive has said the replacement process (which I would imagine involves stripping the existing concrete with heavy machinery) will almost certainly damage a cable that's only trenched 20mm deep, and that Chorus should have trenched it at least 450mm deep. Chorus initially said it had been trenched 600mm deep, but then backed down when it was proved that in places it was only 20mm deep.