When the state was building lightning targets (radio towers and toll booths) they used 40' multipart rods to get down in the water table. All of the buildings in the complex were bonded together (more important than actually being "grounded").
As a similar experience, in my other life, I was presented with the problem of protecting point of sale terminals in dispersed buildings on a property and in some cases buildings that "grew" from several separate ones (separate services). Again our salvation was bonding the whole cludge together with fat wire bonding conductors (4ga or so).
I'm sure the whole mess went up and down with local lightning events but all going up and down together prevented blowing interface cards and that was our objective.
In that regard, think 680 equipotential bonding concepts.
You don't really care what the potential is, only that everything you can touch is the same. Birds on a wire.
