Tom P,
I'm not sure if it is still true, but years ago at Muirfield they told me they had NO automatic irrigation on the greens. They had a single row system in the fairways, but if you wanted to water the greens you had to do it by hand.
Two reasons why:
1. You've got to REALLY want to water to irrigate your greens by hand.
2. You can't do them all at once, so you have to do deep and infrequent irrigation.
Of course that wouldn't work on Poa in Philly.