If the cable is in a concrete channel and the channel is not buried then surely you can just see it.
Probably so, but if the person seeing it is the person who's about to dig the hole then the probably can't just dig the hole somewhere else, unless the designers are sufficiently flexible that they can change the design to allow for it before the stage of attaching the boom or small steelwork. Not as bad as hitting a signalling cable (and the same problem arises if you find a signalling cable in your trial hole) but nonetheless a big problem if it happens any more than occasionally.
For what it's worth I think the problems are (mostly discussed already):
- Rapid DfT go-ahead for schemes based on back-of-envelope estimates by people who didn't really have enough experience of what has gone wrong in the past. The likely reasons for missing the upgrades south of Bedford.
- Not doing the re-signalling before the electrification, suggesting probably that the unrealistic dates as well as the budgets were agreed. If the cables had gone out of use with new signalling then hitting them wouldn't matter. I think there's still quite a bit of 1980s signalling equipment between Sharnbrook and Loughborough, which may come to bite somebody at some point.
- Prioritising schemes based on a rolling stock cascade which in turn was based on the assumption new DMUs would be unavailable or at the least unecomic. This led GWML (releasing lots of commuter/regional DMUs) to have priority over MML (releasing almost none, only Meridians with no obvious role elsewhere). When schemes slipped back most of the new DMUs had to be bought anyway to maintain services in the absence of the cascaded units.
- Inability of the various industry bodies to monitor and challenge emerging standards.
The above are all really down to government making a total change of direction, over a short period spanning the end of Labour and the start of Coalition. The previous policy resulted in lack of electrification experience in the industry, and the later one demanded far too much from it.
The real question is how to get out of this. Hence why I think Bedford to Corby should continue with NR very much in the last chance saloon, along with a thorough independent report (not just one person's opinions like the Gibb report) into what went wrong, how the different teams and schemes did things differently and what would happen if best practice was taken up everywhere. Specifying bi-modes for MML, either just HST replacement and a small growth build or perhaps to replace Meridians too, would give flexibility for the next franchise or the one after that to take advantage of any electrificaiton as it was compmleted. I've suggested on another thread that the alternative of buying 125mph DMUs isn't realistic anyway.