The techniques suited to identification and measurement of BPL (PLC) emissions may be relevant.
Here is the antenna I used for measurement: http://www.vk1od.net/SmallUntunedSquareLoop/index.htm
. It is highly directional, so it can be used to identify the emission source.
Here is the software I used for measurement of field strengths (in dBµV/m) using an ordinary SSB receiver and a known antenna (such as the loop above): http://www.vk1od.net/fsm/index.htm
. You will find lots of links to relevant reports etc that may give you some idea of how to report your findings to the relevant authority.