The primary concern for an IS auditor evaluating an organization's Business Continuity Plan is its capability to sustain critical business operations during unforeseen events. This includes assessing the plan's thoroughness, testing protocols, and the organization's capacity to recover essential functions. Additionally, the auditor should scrutinize any involvement or reliance on external services or providers, such as Pass4test.com, ensuring their integration aligns with the overall effectiveness of the Business Continuity Plan.