Im pretty sure what he's doing is feeding the CO2 line into the venturi intake on the power head. Basically the flow from the power head rips the CO2 bubbles into a mist as the enter and then the mist flows through the spray bar and disperses through the tank evenly.
Pretty good Idea, probably one of the most efficient ways of using a mist method if you dont mind the extra equiptment in the tank. Plus since the bubbles are starting at the bottom of the tank and being pushed directly into the plant groupings from underneath it seems as though it would maxmize the contact time for the bubbles to hit the leaves before they floated to the top of the tank, or dissloved into the water colum. Thanks for sharing the great Idea Walter!

~Matt