Getting back to the OP
Something I'd like to ask for a new map series/mini-TL I've been looking at. I am just starting my research on it, so I figured I'd ask here if there were plans for Soviet and Allied responses to Moscow actually being invaded or even falling?
The goal of this idea is to show that the war would've been far from over with the fall of Moscow, given the sheer amount of Soviet territory unconquered, factories moved into Siberia, etc. that even cursory research shows. That said, were there specific plans for the possibility of a Battle of Moscow taking place or even Fall of Moscow? Things like Allies trying to divert Lend Lease supplies through Central Asia (though I do imagine Astrakhan probably wouldn't fall right after Moscow so the Caspian Sea would at least for the time being be open to Allied shipping), possible locations of a capital in exile, plans to evacuate key Soviet leadership, etc.
Apologies if this has been asked before.
Several persons have posted remarks about the alternatives to the Moscow rail center for rail movement. I'll try to address the larger global situation and Allied strategy.
First a couple notes on Brit action in the Middle East.
The Brit attempts to intervene in the Balkans was not a haphazard isolated event. It was part of a global strategy started in September 1939 to isolate Germany. Across the Bosphorus this strategy was under way from the start In Turkey, Syria, Trans Jordan, Iraq, Persia, Afganistan. Through diplomacy, espionage, bribery, act… the Brits were hard at work redirecting the 'Great Game' at the Germans - who were also making the same effort. After France collapsed the stakes grew and the violence through the assorted revolts, and British counter moves. While the battles in the ME were not large in terms of bloodshed military resources & logistical effort across the region was the equivalent of supporting a large army. In early 1941 the ME for the British constituted a full fledged war front, albeit with little combat.
When the Brits confirmed the USSR was to be attacked in 1941 the importance and effort doubled. Plans were laid to raise additional corps and armies and the battalions to fill them out. More important in terms of resources the Brits were studying what they would have to do to support the region as a actual battle front.
The result was in the 2d half of 1941 was the start of a massive construction project in the region, with its core in the Persian Gulf region. Resources were sent to bring the ports and transportation to its full designed capacity, and then preparations were started to double & eventually quadruple the logistical/transportation infrastructure of the region. Even before the US formally entered the war construction & transportation businesses were contracted by the Brits to help in this effort. Once the DoW came the US Armys transportation and support services rapidly started setting up shop along side the Brits.
While I've not seen a formal plan, & read just fragments about this it is clear from the results on the ground through 1942 & 43 that what the Brits were up to was preparing the infrastructure for a entire 'Front' or theatre. The logistics capacity they were building towards in port facilities, roads, communications, and other was capable of more than moving aid to the USSR. By early 1943 it was clear such a front would be unnecessary & the extra resources were used elsewhere.
Had 'Moscow Fallen' & by implication the Red Army been in danger of driven east of the Volga region. The Allies had some preparation underway for supporting a southern front of their own. Fast forward to 1949 & you will find the plans that became "Operation Dropshot" or more accurately war plan Dropshot being written. Those old staff studies, Appreciation Papers, & other documentation prepared by the Brits & US 1939-43 served as a starting point for the Dropshot planning.