This happened quite a few years ago (I seem to recall about 1966-67).
On a Chevron Chemical Co. site in TN, a 5kv direct burial cable was installed in PVC by the EC. Burial depth was 48”. He felt he was doing the owner a favor in that the cable could be replaced with ease. A few years later, the cable failed. When the lawyers got through, the EC, an upper medium size, was forced out of business. The bottom line was even though the owner OK’ed the installation the EC was liable as he should have known that the amp capacity of the cable buried in earth depended upon the effects of the earth being in contact with the cable. The installation in raceway derated the ampacity of the cable.

Rowdy

Sure looks like it could happen today too. Looking at the code tables for medium voltage cable directly burried, there's lots of language about arrangement, ambient earth temperatue, thermal resistance, and conductor temperature....so how could anyone put direct burial cable in PVC without noticing such concerns?
Back in the 60's the code book (including Article 710) didn't have such language, and applying medium voltage cable would require some concern for what the cable manufacturer had to say about how it was used. There had to be SOME info about the ampacity of the cable...it certainly wasn't included in the code book...and so there must have been something printed up about it by the manufacturer or supplier. I'm amazed that the contractor didn't research this more.

moral of the story, don't do favors.

especially for the oilocracy

Couldn't the contractor just replace the cable for free since he made it so easy for himself to do by installing PVC?