With the new EU legislature, the track management and the Train Operating Companies (TOCs) have to be separated subjects and hence allowing the private sector to enter the market (also called as liberalization of railways). Up to this point, the market was ruled by one TOC (usually the national carrier) subsidized by local government. Its purpose was to provide accessibility and mobility to the general public. However with a new competition entering the industry, the traditional business model has to be adapted to reflect the demand on profitable lines and at the same time provide the basic accessibility and mobility on lines, that are not profitable (subsidized by government). In this paper, we analyze the current planning process of the passenger railway service in the context of demand interaction, including references to the fundamental literature on the topic. Our study shows that the current Train Timetabling Problem (TTP) in the literature does not reflect the actual demand and hence we propose a new problem to be inserted in the planning process: the Ideal Train Timetabling Problem. Such a problem would find the most profitable timetable for each train and would serve as an input to the TTP, in which the feasibility of such timetables would be secured.