I don't have any specific references, but in principle it shouldn't be difficult to model or compute in a 2D way. You need to know either the conductivity or complex permittivity of the medium (at your specific frequency), along with the geometry of the cable. If you can model the cross section of the cable as a couple of point sources, then that makes things easier. Just calculate the electric field from the cable, use that to find the displacement current and then the power loss in the conductive medium. That should give you a number in terms of power loss per meter (or whatever unit) of cable.