Cyber-physical systems are becoming more and more connected as it is the case for the railway domain. This introduces the need for smart monitoring and communication services besides the traditional control-command functions. As a consequence, more complex architectures are required to leverage connected technologies. This challenges traditional processes used to develop such systems. Model-based system engineering (MBSE) has been proposed to tackle this challenge by allowing virtual integration of the system in order to discover flaws earlier in the development process thus reducing rework costs. MBSE requires that several models of the system are conjointly used to assess architectures at different levels of abstraction starting from the overall system level down to specialty domains. However, there is currently a lack of approaches for using these models conjointly to perform virtual integration. In this paper, we present the PST approach allowing seamless integration between systems engineering and real-time specialty domain analyses to support virtual integration. The approach is illustrated with a system from the railway domain; the on-board equipment of the European Train Control System (ETCS).