Sorry ChrisB. Up to now there is not much info about this project. Actually it is still secrete. This video was not an official one and the people from GarageGames replied in their forum that it was not meant to be seen by so many people.

But they also said that they will tell more about that soon.

Which engine is the best? This is very simply: the engine that works best for you is the best. It could be Unity3d on Mac, C4 if you want to have great rendering options, Ogre if you have some good C++ programmers and Torque Game Builder (the 2d engine of Torque) if you want to make a modern 2d game
And it can also be Gamestudio if you want to learn game-development with many examples and with huge community on smaller scaled projects or cartoon games. But you already know this.