Here's my theory, and I honestly think it is correct. Let me know what you think. All right, so each map so far (Green Run and Die Rise) both have their own, specific navcard, and their own, specific navcard table. Now, we know that those navcards save, so if I had the Tranzit one, I would keep it in Die rise and vice versa.
Now, as of right now, neither of those actually work on either map. Neither navcard works on either table. SO, Jimmy said something about waiting and using points to find new secrets. I thnk that his points are MS Points, and they apply to a map pack. Now, each map pack will have its own navcard and table, like the others. Each navcard goes into a table on a different map, so for example, maybe the third one goes into Die Rise.
You might see what I'm getting at. When a navcard gets accepted, to whatever table in whatever map it goes to, we get a new area opened up. So for example, in Tranzit, that would obviously be the second bus route (which I think probably leads to a huge Easter egg tying everything together). In Die Rise, that might reactivate the elevator in the spawn area that can only go to two floors. Maybe grant access to the PhD Flopper?
I would also be willing to bet that, since we see that things can save across maps, we might see a huge Easter egg going across all of the maps that will tie everything together. A lot of things make sense this way. Why would we have nav cards and tables to begin with if they don't work? Why would (so far at least) there be areas that we see could easily be playable (like the second bus route, or the PhD Flopper and maybe another area, like below the elevator) It could link us back to the original four (or three, but instead of Madison we'd have Sam) somehow. What about that interview for the UK PlayStation magazine (look it up on YouTube if you don't know what I'm talking about) where a developer said that death is nit the only ending? I mean, no one really seems to have bought the idea that Transit is over. It just seems too big, there's too many questions otherwise. Maybe I'm wrong, maybe a DLC will just magically open the areas, or an update. But I really think that it relates to the navcards that we haven't found a use for yet.
I truly do believe this is the answer to Zombies. I think that each navcard in each map goes to a specific table in a different map. Now, perhaps I'm not the first person to talk about it (judging by how simple it really is, I wouldn't be surprised), but I would still like to hear your ideas and opinions. Let me know if I am wrong, as I might be. Thanks guys.