@ smucat,
I've yet to see any connection to a meter, but for obvious reasons, only the circuit breaker is visible without dismantling the left hand side of the cabinet.
If you look at an ECI cabinet diagram on the door you will see items such as door alarms and cabinet temperature etc. so I had assumed (but can't confirm) it was those items being transmitted via the telemetry link.
Certainly the door alarms are available in a control room as BT advertise that fact.
Kind regards,
Walter