Why Germany can move units into an Italian controlled East-Poland and collect the NO for not being at war with Russia:
@rulebook:
Noncombat Move
Where Units Can Move
Land Units: A land unit can move into any friendly or
friendly neutral territory, including territories that were
captured in the current turn. It can’t move into or through
a hostile territory (not even one that contains no combat
units but is enemy-controlled) or an unfriendly neutral
or strict neutral territory. If your power isn’t at war, you
can’t move your units into territories belonging to another
friendly power or a friendly neutral.
or
@rulebook:
Noncombat Move
Where Units Can Move
Land Units: A land unit can move into any friendly or friendly
neutral territory, including territories that were captured in the
current turn. It can’t move into or through a hostile territory
(not even one that contains no combat units but is enemy-
controlled) or an unfriendly neutral or strict neutral territory.
Germany is at war (with England …), the territory in question is friendly, because it is Italian. Italy is at war with Russia, but Germany isn’t. So Germany collects the extra income.
The rules concerning a neutral Russia do not apply, as Russia, being at war with Italy, is no longer neutral - not being at war with Germany, as ShadowHAwk correctly pointed out.