Within the comms room it will be possible and is sensible to bond everything together to a common earth - if you had a large hall of kit a mesh might be better, but  a few racks is scarcely that.

Another rack 240m away is essentially out of the EMC zone , and you should assume that the earth voltages could be quite different on a microsecond scale - is it connected by fibre or by twisted pairs to the comms room? (In many ways if you can justify the outlay then fibre makes things much easier. ) Also relevant are the external signals coming in - yo uhave to imagine that they might be at different voltages ,and you do not want anything delicate to end up 'doing the splits' with one interface connected to something at a completely different voltage, The trick then is to marshall the in coming lines such that services are interconnected and therefore not able to be too far apart voltage-wise before they hit the expensive equipment.

If you ever end up designing a nuclear bunker that means all in bound cables for antennas, network cables, power  and so forth have shielding armour that terminates on a common of access panel. For commercial situations the stresses are not so extreme, but the principles are very much the same - you are only trying to prevent overstress of the electronics, and more or less normal ADS.

Within the comms room it will be possible and is sensible to bond everything together to a common earth - if you had a large hall of kit a mesh might be better, but  a few racks is scarcely that.

Another rack 240m away is essentially out of the EMC zone , and you should assume that the earth voltages could be quite different on a microsecond scale - is it connected by fibre or by twisted pairs to the comms room? (In many ways if you can justify the outlay then fibre makes things much easier. ) Also relevant are the external signals coming in - yo uhave to imagine that they might be at different voltages ,and you do not want anything delicate to end up 'doing the splits' with one interface connected to something at a completely different voltage, The trick then is to marshall the in coming lines such that services are interconnected and therefore not able to be too far apart voltage-wise before they hit the expensive equipment.

If you ever end up designing a nuclear bunker that means all in bound cables for antennas, network cables, power  and so forth have shielding armour that terminates on a common of access panel. For commercial situations the stresses are not so extreme, but the principles are very much the same - you are only trying to prevent overstress of the electronics, and more or less normal ADS.