OzarkEdge
Part of the Furniture
Hmm, good question. I guess there should be separate grounding for each house/main central.
It should be the same but it's an old system (houses build 1850ies, electrified 1938, partly renovated in the 1960ies, 80ies and 2012. So there might be strange things in there. I know I have one phase that is quite a lot higher loaded than the other.
That is worth investigating more in any case.. Should get it up on my prio-list...
For your use case, I suspect the Earth Grounds at each building should be bonded together to be at the same potential... to preclude a neutral line voltage difference between the two buildings that might induce ground currents/noise on the interconnecting data cable. Don't quote me, but if you have had issues, this could be something to consider.
OE