When you turn on photo syncing, your mobile photos will be saved to a private section of your Facebook Photos. You can easily share your synced photos on your timeline from desktop, mobile, or another device.Facebook's support site has much more about Photo Sync. Facebook is using background uploads within the Facebook iOS app to move the photos, not anything special with location APIs or Apple's iOS 6 Facebook integration.
Only you can see the photos you’ve synced from your phone. Your photos are saved privately in a section of your Facebook Photos that only you can see. When you view your synced photos, you can choose shots to share or send in a private message.
The app is very clear that all photos uploaded automatically are marked as private and cannot be viewed by others until specifically shared by the user. Users get 2 GB of complimentary photo storage.