If you go to the map page for the South Yaak fire on inciweb, and look at the most recent progression map, you can see that yesterday's growth was all on the north side of the fire. On the southwest and southeast sides, the fire has stopped at forest roads (for now, anyway). Both wind and topography will tend to keep it moving north, away from the river.
The tracks are on the south side of the river, the opposite side from the fire. This is not to say that the fire couldn't become really active on a hot, windy day, and throw sparks high enough that some might land on the south side. In that case, local authorities would probably close roads and rails briefly till things calmed down. It looks unlikely to me that this fire will cause a serious disruption of the EB.