Um, hydrogen fuel cell != pressurized tank of hydrogen
Most sources of hydrogen for fuel cells will probably be from breaking down a hydrocarbon hootch of some sort, stealing the hydrogen and (hopefully) storing the rest for recycling...
http://auto.howstuffworks.com/fuel-cell.htm
If they are trying to make it safe for use in cars, then it probably going to be safe enough to use in a backup generator situation.
/herb