You might have quoted the entire section rather th

You might have quoted the entire section rather than just the part you did. The hydrogen does not mix with gasoline. The 7 works on either gas or hydrogen but not at the same time. There have only been 100 of them made and there are no plans for more at this time. The whole section is:

The BMW Hydrogen 7 burns hydrogen in an internal combustion engine (ICE). When in hydrogen mode, high-pressure injectors, designed by HOERBIGER ValveTec GmbH, directly inject hydrogen gas into the cylinder combustion chamber with pressures of up to 300 bar, (4500 psi). The combustion technique is a combination of spark-ignition and diesel combustion systems using surface ignition, subsequently followed by a diffusion type of combustion. This combustion system matches the efficiency values of the currently best turbodiesel engines at a maximum of 42 percent.[4] The car can also switch seamlessly between hydrogen and gasoline at the touch of a button on the steering wheel, and will do so automatically when one of the fuels is depleted.

The hydrogen fuel is stored in a large, nearly 170 litre (45 gallon),[5] bi-layered and highly insulated tank that stores the fuel as liquid rather than as compressed gas, which BMW says offers 75% more energy per volume as a liquid than compressed gas at 700 bars of pressure.[6] The hydrogen tank’s insulation is under high vacuum in order to keep heat transfer to the hydrogen to a bare minimum, and is purportedly equivalent to a 17-metre (56 ft) thick wall of polystyrene Styrofoam.[7]

To stay a liquid, hydrogen must be super-cooled and maintained at cryogenic temperatures of, at warmest, −253 °C (−423.4 °F). When not using fuel, the Hydrogen 7’s hydrogen tank starts to warm and the hydrogen starts to vaporize. Once the tank’s internal pressure reaches 87 psi, at roughly 17 hours of non-use, the tank will safely vent the building pressure. Over 10–12 days, it will completely lose the contents of the tank because of this.[8]