Cyber-physical energy system (CPES)-complex juxtaposition of multiple energy domains and communication and automation technologies-requires a sophisticated testing framework to achieve holistic assessment and validation, especially at large scale. In this article, the real supervision, control, and data acquisition (SCADA) system of CPES is integrated with the advanced techniques-real-time simulation (RTS) and power-hardware-inthe-loop (PHIL), in a cross-infrastructure manner to create a realistic validation environment for CPES. On the one hand, the method can be applied to extend the capacity of the infrastructures as well as creating a common resource and expertise pool. On the other hand, this approach combines the realistic data and advanced SCADA services with the flexibility of the RTS platform, which provides the possibility to emulate extreme and faulty scenarios with virtual equipment and topology. The proposed approach is demonstrated via a case study of analyzing the impact of communication on advanced voltage and frequency restoration in an isolated microgrid. The case study is implemented on two remote platforms PREDISPRISMES (70 km apart). The validation framework comprises the RTS and PHIL platform coupled with the OPC UA SCADA system in PRISMES, the control algorithm and the communication network simulator located in PREDIS platform.