A new trailer shows off more of SimCity, the upcoming urban planning reboot, introducing how multi-city play will be handled. Here's an explanation:

With Multicity play, you no longer need to provide all the required city infrastructures in one city. Build a police station and share your growing police force with the greater region. Have your friend build a fire station in a neighboring city and soon you’ll see their fire trucks putting out flames in your city. Just like the world around you, neighboring cities support each other through shared resources. These are just a few examples of the Multicity play that you’ll see today in Stone’s gameplay strategy video.

Built from the ground up to be a fully connected experience, Multicity play in SimCity gives you the option to choose how you play. When you login and pick a region, you can decide to claim all the cities for yourself, invite your friends into your region to play alongside you, invite anyone in and make new friends, or join someone else’s region.