Hmmmmm ?? TBH, NS .......... it's either one or the other ......... it's either poly cable shoved through a duct, or armoured cable lain directly in the ground. The only time armoured cable in a duct is utilised is when our contractors get involved
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Believe me, over the many years and working on a semi-rural/semi-urban patch .... I've had quite a few situations akin to MP's circumstance. The cable (as we all know) will unlikely be at the required depth, and even if it had been, years of churning with tractors and trailers can see it become pretty much visible.
I suppose it depends on the level of damage, but I would expect a certain amount of audible noise to be heard on the PSTN side of the circuit if it is 'crushed pairs' causing the problem. The only tru way to ascertain for certain, is to monitor the comings and goings of said tractor and see if it ties in with your graphical data ??
Apologies if anything similar has been mentioned earlier in the thread, I haven't read it all, just the last page.