With the Koralm tunnel, the Semmering base tunnel (SBT) and the Brenner base tunnel, three of the longest and best equipped railway tunnels will go into operation in the intended period of time from 2025 to 2028. One strongly discussed topic in the scope of the safety design of such long railway tunnels is the appropriate choice of fire fighting system. Given the high overall safety standard of the named projects, the question of effectivity and launching of fixed fire fighting systems (FFFS) during the evacuation procedure is not straight foreward, in particular when interactions with additional safety measures, such as smoke extraction systems, have to be considered. To answer this open questions a quantitative risk model is presented which allows for the direct comparison of different design variants, in particular rescue stations with and without a permanently installed FFFS. The application of the developed model on the 27 km long SBT shows that, depending on the surrounding safety equipment in the rescue station, the activation of FFFS does not inevitably lead to decreasing fire consequences for passengers. In fact the activation of the considered high pressure water mist system (HPWM) can have an unvavourable impact on evacuation conditions due to the destruction of a partly formed smoke layer and a consecutive worsening of visibility. The developed model allows for a risk quantification of these influences and a relative comparision of risk reducing measures.