I give it a 50/50 whether the rail bridge will still be usable. Actually I lean toward it still being usable in some capacity. The bridge was fully loaded when the fire occurred and yet didn't collapse, so that is a good sign it retains at least some structural integrity. For an example of a steel structure which lost integrity under load see the World Trade Center. I am unable to determine offhandedly from the photos if it suffered severe damage, I can certainly see cosmetic damage but I can't tell about the structural elements. Steel is a very resilient material, the most resilient of all civil engineering materials. It is also very predictable, which is actually its main selling point aside from cost. You know if it is going to fail because there will be groaning and necking, and it is possible to determine if it left its elastic strain zone. If the fire caused the steel to lose 75% of its strength, and it had a factor of safety of 4, then nothing happened although its lifecycle was probably reduced from 100 million train loadings to 1 or 10 million train loadings. If the steel didn't get hot enough to become fully molten, then its crystal structure didn't change. Yes temperature differentials are bad, but in a military operation the bridge can be operated at a much lower margin of safety than in peace time and still be considered acceptable.
The rail bridge appears to be steel beams on reinforced concrete columns. I doubt the columns were impacted much but who knows. IMO the weak point is likely to be the connection between the beams and columns but who knows.
Fun fact for the road bridge: reinforced concrete beams are only economical for spans up to about 20ft / 6m maximum. After that they must be prestressed. Pre-tensioned precast spans are typical up to the longest transportable length which is about 58 ft / 18m. Beyond that they must be post-tensioned cast-in-place, although anything shorter can be pre- or post-tensioned or precast if it makes sense for the design.