If you're curious what the Spec Ops writer was trying to do with the game, this is a great interview:

http://www.gamespot.com/features/gamespot-gameplay-special-edition-spoilercast-spec-ops-the-line-6386587/

He doesn't shy away from answering direct questions, like which parts were hallucinations and which were real. Kinda refreshing to hear a writer willing to lay it out there.