I would call any reading less than 20 megohms no good. With 1 to 3 megs, I think it's fair to say that the insulation is compromised in one or several other places. Not so uncommon with direct-bury, in my experience. They'll get to revisit this problem down the road. Maybe not this week or next, but perhaps in a few years.
Just curious, did you megger them at 500 volts?
Just curious, did you megger them at 500 volts?