User blog comment:Pauolo/Missing texts and unused content/@comment-25082029-20140727202159/@comment-1500935-20140729103528

Subtitles are not written among the other texts appearing in-game (location names on maps, texts in menus, and others). I think subtitles are coded among other files like those used for maps, or even directly the sound files used by the game. Unfortunately that would require extraction knowledge which I don't have. However I can recommend you to contact Gildor, the creator of the umodel viewer and extraction tools. He knows his way around games using various versions of the Unreal Engine and helped me to get texts from BioShock 2 which were coded directly on map files.

Btw I think you're right to expect a bit of lore from the subtitles. I went through the game and its DLC several times a few months ago to write down each and every announcements made on loudspeaker and some were pretty much interesting. Even so, some dialogs in Daud's missions helped to place them in the continuity of the main game.

Anyway, I hope Gildor can help you on getting to the subtitles.