Metered faucets can be used on a project pursuing this credit, but the LEED baseline for faucets is so stringent it will be tough to contribute much to the credit threshold in this way. Using toilets, urinals, and showers to earn the credit will be more important, as well as possible water reuse.
See additional guideline information from USGBC - It seems the baseline .25 gal per cycle can apparently be reduced in design case to 0.1 if you use .5 gpm @ 12 second cycle (the average cycle time for autocontrol faucets). This was adequate on my project to reduce beyond the 40% reduction, thereby eliminating the need for a $90,000 rainwater harvesting system to achieve 11 points.
http://www.usgbc.org/ShowFile.aspx?DocumentID=6493