A widespread and long-lasting power outage, i.e., blackout, is one of the most severe threats for society at a national level and possibly evolving to an international incident. Due to the cross-sectoral function of electrical energy, almost all parts of society will be directly affected by a blackout, including most of the critical infrastructures (CIs) in the concerned regions. Therefore, relevant measures to prepare for and to recover from a blackout require structural coordination in advance between national government, municipalities, local authorities, and the CI. In late 2022, a comprehensive strategic exercise (BlackAUT) has been carried out by the Competence Center for a Safe & Secure Austria (KSOe), the Austrian Institute of Technology (AIT) and the Federation of Austrian Industries (IV) in Austria, involving about 80 experts from CI operators of multiple domains and the public administration. Additionally, a Cascading Effects Simulation (CES) was implemented as part of the strategic exercise to provide the participants a better overview on the potential side effects a blackout might have throughout the country. In this paper, we present an overview on the scenario setting, describe the integration and aimed benefits of the CES. We will discuss in detail the main reactions of the CI operators from the different domains, highlight particular dependencies among them that have been identified during the exercise and sketch the main findings and take-aways from this strategic exercise. As a main result, we will discuss the future implications these findings have on the preparation efforts to increase the resilience of critical infrastructures in Austria and all over Europe.