What is a condition under which the physical security plan of a transmission facility may require third-party review?

The correct answer highlights that the physical security plan of a transmission facility may require third-party review if it is deemed critical by applicable coordinators. This condition is significant because it emphasizes the need for an objective evaluation of security measures, particularly when there are substantial changes in the facility's operational environment or when vulnerabilities are identified. In cases where coordinators identify risks that could impact system reliability, a third-party review helps ensure that the security measures in place are adequate and robust.

Regular reviews by third-party entities can enhance the security posture of facilities by providing an outside perspective on security plans, ensuring compliance with regulatory requirements, and identifying potential weaknesses that internal teams might overlook due to familiarity or bias.

The other options suggest scenarios that do not universally apply to the requirement for third-party review. For example, having a new manager appointed or responding to unauthorized access incidents may prompt reassessments of security practices but are not standard triggers for requiring a third-party review. Similarly, relying solely on scheduled audits does not account for the dynamic nature of security needs that a critical designation could necessitate. Thus, the need for continuous assessment by external reviewers is crucial for maintaining high standards in physical security, especially in high-risk environments.