base-T means the connection is on a bus, with a coaxial shielded wire

most ethernet cables are "UTP" or unshielded twisted pair, and these are not used in situations where the cable passes a high EMF source or if leaking signal might allow a tap to be non-invasively applied - and for this anyway the reason why almost everything is encrypted now as this closes up this vulnerability, but it does still give traffic volume information even if none of it can be decoded, and the headers have naked IP addresses, but ultimately security is busted if physical is gone (one of the first rules of signals intelligence, never send a message if its interception informs the enemy in any way or might be a weakly protected message)