One note for any work set in early 1870s Paris: the entire city has been convulsed for the last decade by the Haussmann renovations, which have carved railroads and the wide boulevards we associate with Paris today through neighborhoods that had previously been dense networks of medieval alleyways. Haussmann affected the largest peacetime urban destruction on any city prior to Robert Moses-era New York; his critics condemn him for the wanton destruction of Old Paris, while his defenders (unlike Robert Moses, he has many) point out that the rapidly industrializing Paris of the time is incapable of sustaining itself without a high capacity distribution system for food and other raw materials imported from the countryside.

Of course, with the Prussian Army ringing the city and cutting off supplies (it's a siege, after all), that's less of an issue; sure, what supplies the city has can be efficiently ferried back and forth, but eventually the city is going to starve.

Or not. On further thought, we can run with your Cold War analogy and introduce the Berlin Airlift: a Royal Navy-led operation to supply Paris through the use of ironclad blockade runners escorted by river monitors up the Seine from Entente-held Rouen. At that point, efficient distribution of the barely-adequate supplies (both to feed the civilian population and to keep the army functional enough to keep the Prussians out) becomes critical, and enter the mainframe, a top secret project, solving the complex problems of rationing and distributing food, coal, etc.