Response from the site administrator
Supports Xcode .atlas for SpriteKit. Will even automatically create an atlas at runtime if one doesn't exist for a "collection of images" tileset.
For Cocos2D, TexturePacker .plist atlases (and compatible, ie Zwoptex) are supported. If there's no atlas for a "collection of images" tileset you'll receive a warning in the log (it's a performance issue).
There's no TexturePacker support for SpriteKit though. It's probably not very common, and difficult to add. If you really need this, please request it.