Battery energy storage systems (BESS) play an important role in power systems with high shares of variable renewable generation. Modern BESS have control functions for the provision of all types of reliability, stability and resiliency services to the grid. In this paper we present a real-world experience of using a megawatt-scale BESS with grid-following (GFL) and grid-forming (GFM) controls and a run-of-river (ROR) hydropower plant to restore a regional power system after blackout event. We conducted power-hardware-in-the-loop experiments integrating a real synchronous generator with real GFL/GFM BESS and loads. Both simulation and experimental results presented in this paper show the different roles and locational impacts of BESS with GFL or GFM control when restoring a segment of power system after blackout. The results provide further insight for system operators and utilities on how GFL- or GFM controlled BESS can enhance grid stability and how a ROR hydropower plant can be converted into a black-start-capable unit with the support of a small-capacity BESS. It shows that a ROR hydropower plant combined with a BESS has a potential of becoming one of enabling elements to perform bottom-up black-start schemes as opposed to conventional bottom-down approach; thus, enhancing the system resiliency and robustness.