An accurate enquiry can say that the rear boundary is inaccessible or that nobody knows which energiser serves a section. Those are practical issues to resolve, not details to guess. Ask the responsible owner or manager for access and existing records. An inspection should make its limits clear if the relevant installation cannot be fully reached.
For a shared-perimeter request, use a consistent way to identify sections, such as the managing team's existing references. Do not publish a detailed security layout in a public enquiry. For the private property record, retain enough information to connect the certificate and later repairs to the actual system, while keeping operational access information with authorised people.