Today, GNSS-based solutions (Global Navigation Satellite Systems) facilitate the implementation of the train localisation function on-board the vehicle. In the railway context, as a train has to travel different zones on its itinerary, multiple obstacles in these environments can cause different signal perturbations: multipaths, signal delays and masking phenomena that lead to negative consequences on the position accuracy. To reinforce the position quality, a localisation system, developed in the GaLoROI european Project and based on the combination of sensors such as a GNSS receiver and an Eddy Current Sensor, is studied. In this paper, we present a procedure and a model, which aims at evaluating the dependability of this system under local impacts of different railway environments. It allows us analysing complex behaviours of the sensor fusion component on the availability and accuracy of data provided by GNSS & ECS sub-systems and also to take into account the reliability parameters of hardware components.