There were two transport plans the heavy bombers operating out of Britain participated in.
1) Mid 1944, To degrade the French transport system and isolate the Normandy Area
2) Mid/late 1944 on, to degrade the German transport system.
For 1 the strikes on marshalling yards were the least cost effective as noted, through lines could be patched together quite quickly and German military trains tended to be made up in Germany and made a loop into France and return.
For 2 the strikes on marshalling yards were highly effective as that is where trains were made up and dispersed, changing a bulk shipment from one supplier into deliveries for its multiple customers. If this cannot be done the economy slows and even stops.
Organization Todt (including RAD and NSKK) had 70 to 90,000 workers in France 1 June 1944. As German forces retreated many of the trained rail personnel that had been running the much wider 1942 network were still available for deployment in Germany.
According to the British Bombing Survey unit traffic on the French west rail system halved April/May 1944, down to 20% on D-Day, 1% on 1 July. The Reichsbahn went from 15 billion ton-km mid 1944 to under 9 billion end of year when the allies were mostly attacking the western part of the system.
Few targets were destroyed by bombing, if the other side retained possession things could be repaired. Most bombed installations were brought back on line, regardless of who did the bombing. It was one of the weak points in the campaign, firstly recognising how little damage the bombs that hit actually did, then how quickly the damage could be repaired, then having the strength to be able to hit new targets as well as keep the previous targets suppressed.
USSBS, The How and Why Air attacks crippled the German Oil-Chemical Industry
"The Leuna versus Allied air forces bout resembled in some ways a prize fight. The plant was knocked down nine times but never out, and recovered rapidly at first but more slowly as the accumulating punishment began to tell. Its recovery capacity also slackened as indicated by the decreasing percentages of the recovery plans. It might be said that the plant was finally defeated on points. To have achieved a complete knockout the Allied air forces would have had to destroy its recovery capacity, and they did not deliver a sufficiently strong punch to accomplish this." The Germans only abandoned repairs on 1 or 2 oil refineries.
See the book The Collapse of the German War Economy 1944-45, Allied Airpower and the German National Railway by Mierzejewski. It documents the decline of the German Rail system in late 1944 and early 1945 to the point where it could not even supply its own locomotives with coal, where special derail gangs were formed with quotas of cars to derail each day to clear congestion. Where the German economy was collapsing, mainly due to the transportation strikes, the canals, the railways and the oil. How the stocks were run down and weapons that were made were stuck at the factories. Tables give an idea of the run down in coal production. The book makes the case the marshalling yards were the key.
See also A Forgotten Offensive: RAF Coastal Command Anti Shipping Campaign 1940-45 by Goulter. In particular the last chapter on the economic effects of cutting off most of the Scandinavian iron ore trade in late 1944, it helped but the Germans had stocks to keep going for a while. The tables give the decline in steel production. If ever there was a sustained strike against a vital raw material it was the anti shipping operations against the ore ships from Narvik.