I'll walk though what makes me think it's real.
The first thing is this new gun. I can see Mr. Vonderhaar saying it right now: "With Black Ops 2, we are doing something brand new, never before seen in Call of Duty. Anyone who buys the Season Pass can get a new SMG not available to anyone else." It recon it won't be very good, just some reskinned other SMG, with an effect like the AN-94 to keep it interesting. It's a great idea to keep people interested though, and a great marketing ploy.
The second thing is how real the maps look. They stick true to that "Just a small hint" thing that Treyarch has. Grind is a skatepark, and the hint is the half pipe and dudes doing parkour. Mirage looks like some kind of oasis in the sand. Downhill is some kind of ski resort log cabin, and Hyrdo would be a dam. The art style fits with the release and promotional artwork for the game, too.
Now then. Zombies.
Die Rise. The name clearly plays homage to Der Riese. But say it. Die. Rise.
High Rise. look at the buildings. High rise apartment complexes. A nice, clever play on words there. It's not a remake of anything, but a new map all together. Lots of tight buildings to weave though. Offices, flats, stores on ground level. There looks to be crosses in the picture, so perhaps a graveyard. Perhaps broken roads between areas.
Yes. Areas. I think it could be a Tranzit map.
Look behind the middle zombie. What's that in the sky? Looks like a Helicopter to me. This could be the new replacement for the Bus. It would take you from rooftop to rooftop. I hit a snag with the idea though. Zombies attack the bus on Green Run. How would they jump on a helicopter? The solution is rather simple: A broken robot pilot, like the broken bus driver. He can't very well see the broken, fallen down buildings, and so veers near the rooftops, letting zombies jump up and on the helicopter. Upgrades might not happen for the chopper, but perhaps a buildable Gatling Gun, that when it overheats it breaks up, and the parts respawn, like with the Jet Gun.
As for the Easter Egg, I can see an easy story. The Tower in Green Run has no special properties other than it's the only tower standing in the area. I don't think the tower itself matters, just that it can conduct power and is tall, and perhaps it needs to be somewhere specific geographically. With this in mind, you can get some tall apartment structures that have radio towers on the top of them. You would likely have to do a similar sequence of events and power the tower, and pick either side again.