The same thing happens in Shogo and F.E.A.R. with Armacham. There are even hidden rooms in fear with odd coloured walls and the ginger fat bloke standing in the middle of the room with the main theme from Shogo blaring away. Is a little strange.

Seriously, no one here has read about this before? It's intentional, they are trying to keep their games in the same universe, though often at drastically different times/locations.
I think I read about it on RPS.

You didn't know?
I found it kind of cool.

It's true, we're all traveling through time, right now.

I'm moving at a rate of one second per second.

It's neat, I wish more games were connected in subtle ways.
I remember watching Predator 2 as a teenager and flipping the heck out when I saw that Alien skull in the Predator's trophy room.