I definately see the soviet influence. For the Motherland! The subtle duo tone works very well, I haven't looked into propaganda posters much just yet but I guess the simple colours were for ease of printing right? The alignment between the top of the broadcast tower and the top of the mike works well also.
I haven't done much research either, but I can guess.
If you want to cover your country in propoganda posters, you're gonna use the cheapest method possible. You're also dealing with a wide range of literacy, and you've got to stand out next to local advertising.
Net result: Bold, simple, a few bright colours, using your national colours.