If I understand: they add an electric motor to the (output?) of the transmission. Its purpose is to get the car moving. When up to speed the engine is started and spun to the right speed, and then is mated to the transmission. The "gain" is loss of weight from removing the heavy clutch, and perhaps 1st&reverse components.
Not a bad idea, although the battery pack has to be hefty enough, and a "large" electric motor has to be added. Still, as one more method of coupling engine to road it makes sense to me: a hybrid method for city-esqe driving, but direct coupled ICE for the upper speeds. Prius does quite well on its hybrid approach but this sort of approach would be more optimized for the open road (no need to circulate power between mechanical to electrical to mechanical). I believe VW had a similar idea, albeit with a single gear ratio.