Not being an electrician or contractor I wonder if this is common knowledge or not
I was speaking to a supplier the other day about installing an electrical component at a remote rural site and mentioned that the item would not work if the cable was stolen?
Apparently the preferred method of cable theft is to dig a hole until you find the cable then attach it to a vehicle and drive along the line of the trench until you have pulled up as much cable as possible.
He said he had just heard from another contractor that when you lay the cable, cover it with a 150mm layer of soil and gravel then pour thinned tar into the trench.
Apparently it forms a conglomerate around the cable and makes it impossible to pull up or out, the cable just breaks off when it reaches the end of the section excavated, which is usually a few meters depending on the size of the hole.
Sure it won't stop thieves from trying, but because it will require extensive excavation and the fear of being discovered before they remove enough to make it worth their while, they move on to easier pickings.
For you it means replacing a short length of cable instead of shelling out for another one or two hundred meters with all the required excavation etc. and the cost of the tar is a fraction of replacing the cable.