Minecart with Dispenser

Minecarts with Dispensers are unimplemented vehicles that, as the name implies, are minecarts with Dispensers in them.

Other than the screenshot shown below, no detail about its use, function, or activation method were published.

Trivia

 * In 1.5, ability was added so with third party programs, you can put any block in a minecart, and Dinnerbone was most likely demonstrating that functionality with the dispenser cart

Theory
This is a theory about what minecarts with dispensers do. They shoot whatever is in them when they touch an activator rail.