I think the safety officer meant that white paint prevents the rail from heating up. The heating of rails contributes to problems with derailment. If the heat isn't a contributor, that heat is one less thing you have to fight (as in account for).
But the photo caption paraphrases him and says that the white paint fights (as in prevents) the heat, which uses similar words but a different logic to it (but the same overall meaning).
If I've got that right, then I think the blame lies on whoever wrote this article for making it confusing.
Reflecting the sun means the rail no longer has to fight the sun's heat.
Without the paint, the sun heats the rail and heat expansion fights against the elements holding the rail in place until the rail cools down or something moves. If the something moves, trains can derail.
But that's backwards. I took it to mean the rails or the engineers are no longer fighting (coping with) heat input from the sun because the rail never receives that heat when it's reflected away by the paint.
I know what it means. "you're not fighting the sun's heat" means "the paint is fighting the sun's heat" but that's no explanation of how it could mean that. I say it's backwards because clearly whatever's doing the fighting is not the paint because it has the opposite effect. It must be the steel, as you say, or the people struggling with the problem.
But the photo caption paraphrases him and says that the white paint fights (as in prevents) the heat, which uses similar words but a different logic to it (but the same overall meaning).
If I've got that right, then I think the blame lies on whoever wrote this article for making it confusing.