Three Are Better Than One
03/11/2006 Correction. I spoke with a fire fighter. These are not stand pipes and they are not fire hydrants. They are sort of the opposite. You put water into these instead of taking water out. These probably connect to the sprinkler system inside this building. If too many sprinkler heads go off in a fire, there may not be enough water from the normal source to supply all the sprinkler heads. Fire fighters can pump more water into the system through these.
If I've still got this wrong, I hope a fire fighter or someone who knows will post a correction.