Yes, it is unacceptable.
There seems to be two possibilities - one is that the cable runs date to the BR period and that practice on the Western Region at the time was not to bother recording it in the first place and not to use the concrete troughing found elsewhere either. If this is so, it is highly likely that whoever made or endorsed the decision is no longer even alive. They certainly won't be still working for the railway.
The other is that this is yet another case of Railtrack failing to retain and maintain records, and where there were no records, failing to ensure that personal knowledge was passed on to the next generation. Now many would think that former Railtrack board members richly deserve being held accountable and penalised, just for existing, but I don't think any of them are still working for the railway either (who'd want them?).
It's lucky that some of use have long memories and a pity that the story keeps needing to be repeated.
In the late 1950s and early 1960s a start was made on re-signalling the GW with multiple aspect signals to replace the Semaphores and Searchlight signal used by the real GWR. The cabling was installed in concrete troughs along the route.
Then, as now, there were people who could see their way to a few bob by nicking the signalling cable out of the troughs. It was even easier than pinching the open wire telephone lines as there was no need to climb the poles.
As a quick solution the WR signal engineers ploughed the cables into the ground using a rail mounted thingy. The position was known - the furthest from the track it could be was defined by the working range of the rail mounted thingy.
In the 50 years,
repeat 50 years, since then tracks have been realigned and layouts changed. No doubt some of the cables have been moved as well.
NONE OF THIS MATTERED until electrification reared its ugly head some 10 years ago.
Only since the decision was made to electrify the line has the position of these cables become important.
It is NOT that the original decision was misguided or wrong - it's just it would have been better to have completed an accurate and complete cable survey before piling for the overhead masts started.
And also, many old records are indicative only. I had occasion to have some work done on the foul and surface water drains from my house some years ago. The water company's records - made in 1920 as the house was built - showed that both drains existed. The snag was they were 6 feet away from the position marked.
So all these posters ranting about incompetent record keeping should keep quiet and give thanks they are not responsible for 500 miles of 175 year old trackside.