There is a file at NARA called SOVIET UNION, SURVEY OF THE RECORDS OF THE BAND I (NR 3708 CBTM13 20293A 19420201).
It is a German estimate of Soviet industrial production in 1942. I assume that some of the information on this report comes from monitoring the internal radio and radio-teletype traffic between industrial centers.
It would be interesting to compare the data on this report (and others like it) with the ‘official’ numbers from Soviet/Russian sources. Unfortunately I could only copy the first pages of this large report (~300 pages):