Cooperative, connected and automated mobility (CCAM) across Europe requires efficient and coordinated solutions to overcome cross-borders service discontinuity. The provision of CCAM services across different countries has enormous innovative business potential. However, ensuring uninterrupted connectivity poses technical challenges that 5G technologies aim to solve. In the mark of the 5G-CARMEN project, good progress has been made to develop wireless infrastructure technologies for 5G deployment at the cross-borders. However, besides the field trials, testing the performance and limits of connected vehicles technology to enable safer real-world deployment is a real necessity, particularly, when considering fully autonomous driving vehicles. Digital Twin represents an innovative solution that provides a software replica of the 5G physical network allowing the study and optimization of real-world use cases. This paper presents a simulation-based digital twin developed to emulate connected automated and autonomous vehicles performing cooperative lane change/merge maneuvers, as defined in 5G-CARMEN, in a cross-border scenario.