While it may seem prudent to be concerned about a fire potentially threatening a train...
...Reality is it just isn't going to happen. And both the Camp Fire and Carr Fire of 2018 are primary examples of why. A trackside fire will not be an issue for Amtrak; unless it just started (and thus is very small) the moment the 911 system is activated for a response, a call is made to the respective railroad dispatch and that section of track is immediately closed. All signals drop to red and all trains, no matter their priority, grind to a halt. Fire engines arrive at the scene and 99.9% of the time have the fire controlled in minutes. Unless the track infrastructure is damaged, another call is made to the railroad dispatcher and trains are allowed to proceed (at a reduced speed) through the area until all firefighting personnel are out of the area. If damage did occur, then track inspectors are sent out and repairs are made.
If the fire turns into a major incident, trains will reverse direction (just because there isn't a locomotive on the rear does not mean it cannot back up; a crew member will just be placed on the rear and guide the engineer by radio at a reduced speed in the opposite direction) and proceed clear of the danger area. Both the Carr and Camp fires affected major rail lines (UP and BNSF respectively). By the time the fire got close to the lines themselves, nothing equipment-wise was anywhere near the flames.
The only threat to passengers is a cancelled trip.