This stuff popped up a few months ago, and the original source was as reliable as someone quoting their brother's friend's wife's brother's plumber. Just looks like dull and generic mod concept art to me, random urban decay and a few uninspired combine alternatives. Even if by some long stretch it was from a real project, it is completely irrelevant now.
I recall the early concept art for Combine overwatch were dressed in trenchcoats based off the Nazi Army. I saw the last pic showing a metrocop wearing a German WW2 style helmet. So its likely these are old stuff for Half Life 2.