This paper delves into the application of Digital Twin Technology (DTT) in the digitalization of assets, processes, and services to improve maintenance performance in railway applications in the context of European Regulation EU 779/2019. Digitalization plays a pivotal role in certifying the suitability of rolling stock in the railway sector. The primary objective of this study is to meticulously examine the fundamental tasks required to build a digital twin in this specific context. The process involves the contributions of key entities fulfilling specific roles: the maintenance and asset certification service provider ensures the integrity and compliance of rolling stock; specialists in IoT and process automation, along with experts in software platforms and services, are tasked with implementing the technological aspects of the digital twin; specialists in BIM technology contribute to the modeling and information layers that are pivotal in the context of railway digitalization. This paper delineates critical stages, from data acquisition and management to model creation and information integration, highlighting the crucial role of DTT in this process. Furthermore, the challenge of digitalization in situations where assets and processes are in an initial state of low or non-existent digitalization is underscored. A profound understanding of digital assets, information layers, and underlying models becomes crucial in the context of the current challenges of railway digitalization.