Thanks for the input, but I think all associated networking equipment got ether-fried.

I pulled the BBB's out and slipped them a known good micro-SD Debian image, no joy. The router and the switch they were connected to are also
ether-fried, as well as a workstation on that network.
Nobody talks ethernet anymore. Maybe running the miners at 240vAC and connecting them to some 120vAC networking equipment
connected by a long cable to a different 120vAC circuit and then to the utilities
caused some of it to capture a *lot* of energy from the lightning.

 
Luckily I have 2 more BBB's, I'll re-image them and see if I can get them running again.
This time I'll get some grounding and surge protection for the ethernet.
Was  using older, hand-me-down equipment in an industrial area, was bound to run into some problems eventually.