So the answer is:
This connection is a typical choke input filter even though the choke is situated in an unusual place.
Same circuitry is presented in Radiotron Designer's Handbook 4 Edition at page 1163 (fig. 30.1G). Here the choke is also located between ground and the center tap of power transformer.
I've downloaded RDH4 from Pete Millet's site and here is the figure 30.1G