Many studies had been made on optimization problems related to the maintenance operation works in the railway world. In this paper, we focus on lesser-known type of these problems. Here, the maintenance is already scheduled and the infrastructure manager can only change the train timetables and the routing. This problem is not well treated in the literature. In this work, we define the problem and we present a model. Since several days are available to solve the problem, the level of abstraction of the model and the size of the considered instances let us use an exact method. We propose a Mixed Integer Linear Program minimizing the primary delays. Results on real world instances are reported.