Back2Fronts is an extensive mod that will overhaul your Call of Duty 2 game to a next level. This mod brings more variety, intensity, realism and battle-like experience. Try new weapons, fight new enemies, fulfil new missions and explore new options. Mod is SP and MP friendly (although primary part is SP).
The Downtown Assault map contains a part where Lt. Volsky mans a machine gun to help cover a russian engineer squad. The two windows with machine guns now hold a Maxim and a DP-28.
maxim!! :DD
but those are german positions, i think mg34/42 actually would fit here
Stalingrad battle is know for fact that buildings changed its ownership several times per day. Plus, in the plot of this mission you are told by Lt.Voslky that Germans captured few buidling blocks and you must retake them back. So you are actually fighting for lost ground - hence the Soviet equipment in "German" territory.