Mazda has already made some hydrogen powered RX8 concepts powered by hydrogen. They say that their Wankel rotary engines are perfect for hydrogen as the heat generated does not hinder their performance. According to this article, the high temperatures do not cause a pre-ignition problem, sometimes referred to as "pinging" in piston engines.
Now Mazda engineers have placed a rotary engine in their Mazda 5 model, a small wagon that is sold here in the States. The rotary engine can run on hydrogen or standard gas. Additionally, they have added an electric motor to the vehicle, making this a gas/hydrogen/electric hybrid... or should I say "tribrid" - perhaps not.
This vehicle is their second attempt at hybrid vehicles, with their Tribute SUV using the same hybrid gas/electric system developed by Ford. This is also their second hydrogen/gas foray, as they have converted some of their RX8 rotary vehicles to hydrogen power. This is their first vehicle combining both.
[Source: Auto Industry U.K.]