Its called digging - where the cables are will have had the earth turned over to a much greater depth than most other places in the garden (assuming your codes are like ours and require a minimum of 900mm depth for cables).
This turned earth will have several effects
* improved drainage
* organ material to a greater depth (top soil backfilled into the trench)
* improved aeration
* breaking of clay pan (if you have that type of soil)
These effects can last for over 10 years - in with the case of clay pan will last for over 20 years.
Unfortunately there is also a likelyhood of suffering degraded growing conditions although this is rare.
I'm interested in the current density that is required for the coaxial electrodes though - and can the system also be monitored to track soil moisture for an automated watering system?