That may happen, but it's not the case here. The project was written using modern standard sizes, as required by law; but knowing that the tunnels are ancient,

That may happen, but it's not the case here. The project was written using modern standard sizes, as required by law; but knowing that the tunnels are ancient, they also mandated the provider to make a field study to figure out the real tunnel minimum sizes, and build the trains according to its result. The scandal happened when this caused a delay in the initial estimated dates, and politicians found out that they wouldn't be able to open the train lines in time for this year's elections.