Sunline definitely has a consistent system, and the "hythane" mixture sounds quite promising to me for bus applications.

Considering that hydrogen has more than twice the energy density of diesel fuel, it may cost twice the price of diesel (per kg), and still be economic.

I found two documents from Alstom about the iLINT (in German language): the "Press Kit" and a product sheet.

They claim that the hydrogen tanks were safer in a collision than a "regular" fuel tank. According to some source I read, the hydrogen tanks are the same as used on hydrogen buses.

The hydrogen tanks and fuel cells are on the roof of the vehicles, whereas the "traction block" (DC-DC converter, control electronics, and motor and gears use up the space previously used by the diesel motors and gearbox. The batteries and replaced auxiliary equipment is stowed in the other space used for a third diesel motor traction block (as mentioned previously, the LINT 54 has three traction blocks). The passenger space could remain unchanged. Actually, Alstom's chief for Germany apparently is quoted that this train is "frighteningly non-spectacular"…