I don’t think railroad tracks were high priority targets for the Luftwaffe. Nazi planes mostly attacked Russian troops and cities like Moscow and Leningrad. One problem with bombing tracks is that they were hard to hit with the “dumb bombs” of those days–if bombs missed the tracks by just a few meters, all they did was sprinkle dirt over them–also repairs were relatively easy, so in most cases bombing may not have been deemed worthwhile.
Another problem is that the Lutwaffe in Russia was hard pressed to keep aircraft operational, and supplied. It may not have been able to spare the planes for a systematic bombing assault against the red railway system.
Yet another consideration, during the height of the Luftwaffe in Russia in 1941 and 1942, was German belief in a quick victory, won by conquest by the army. Since the Germans assumed they would overrun Russia, there may not have appeared to be much need for bombing railroads–the whole country would fall into nazi hands soon anyway–or so they thought.
The Red Army depended greatly on railroads for strategic mobility and logistical support.
The western Allies DID send many planes to pound german railroads. They had vastly greater numbers of bombers than the reich and could spare great numbers of them for such targets.