Holy fucking shit that was absolutely beautiful Gavin. Not only have you captured the feel of the game exceedingly well, both in the style of music used for each 'area' of the game (Columbia, the racism, the Luteces, Elizabeth and Songbird etc.) you seemed to capture one of the core mechanics of the game within the song itself: the callback to Little Sister seems more than a little reminiscent of Albert Fink's use of Tears in the game world, taking music from other universes (in this case Little Sister, your Bioshock song) and using them himself.
Also, was that CAGE with Songbird take me home?
Some people might think that there was too many ideas and styles in the song but it fit the tone of the game, as your songs often do. Lots of ideas, lots of different styles, sudden changes in tone/theme.
Absolutely fucking excellent. Congratulations once more.