I've been paying attention to standpipe and sprinkler connections for quite some time now, but it wasn't until today that I started seeing (or noticing) little faucets on some of them. I'm not sure, but I think they allow the connecting pipes inside the building to be drained after being used or tested.
Day 677
Standpipe spigot
November 6th, 2013
Maybe these are wet standpipes?