I didn't hear the podcast but I am downloading it now. The idea is intriguing.
I have watched videos of jetting a well, and if I recall correctly it has a depth limit of 10-12 feet, probably determined by the volume and velocity of the water. I am curious what type of organic matter would be used for the wicking. I am thinking of a mix of sterilized
compost and sawdust. Sterilized so you don't introduce bacteria to the water table. In my theory the tree would send down a taproot/feeder root through the most fertile substance and when that food was exhausted it would send out feeder roots through the normal topsoil zone resulting in a drought tolerant deep taprooted tree.