The official Citizen Zero site has posted a new "ramble" all about NPC's in the game.  Here is a snippet from the post:

CZ uses a simple "cinematic" interaction mode. When you select the NPC and enter the dialogue mode, we move the camera and fade out other characters around you so that the NPC can use gestures and body language to covey their attitude and changes in their attitude as the result of your conversational choices. This means that if there is a mob of PCs hanging around the NPC your encounter with the NPC still feels personal. The game uses a very simple dialogue-based menu. The text will vary from NPC to NPC but the options all relate to two things: An attempt to alter the NPC's attitude (bribery, charm, blackmail) A request for a service from the NPC We considered using more complex RPG-style dialogue trees but they are best suited to static hand-crafted story-driven content and our game has a much more open-ended story system. Voice over is provided for NPC greetings and goodbyes to give personality to the NPCs. The style varies from type of NPC to NPC but you are dealing with generally rather dodgy characters, giving the game a gritty frontier or "Thieves' World" feel.

You can check out the full article at this link.