Planetside: Core Combat is now officially on live servers! Anyone who has the expansion can now enter and explore the new caverns, vehicles, and weapons. Here's a post from Sporkfire:

The PlanetSide servers will be brought down tomorrow morning at 3 AM Pacific (this morning) for the Core Combat update. There will be no client patch accompanying this update. Once the update is completed, the caverns of Core Combat will be open to those who have the expansion.