Martin Potter wrote:

An interesting point! And did this underground system radiate at HF??
...
... Martin VE3OAT

Martin:

It is the house lines which have some amateurs worried, unless you have
an underground home, or all lines are run through properly shielded
conduit (NOT likely!), this is what worries most amateurs ...

Although I use 10/11 meters daily and 80 meters 2/3 times a week, most
of my operations have moved vhf/uhf/shf. I think that is the future.
HF simply servers too few to demand the consideration some wish.

Regards,
JS