Marc, are there any roughly known numbers how Poa gets in; ie what % is by birds, golfers shoes, wind? From my experience i see a definite pattern of poa ingress from the edges of the greens, anyone else noted this?
I played in Mexico once and the superintendent Eddy Mena worked on the principle of 'dont leave any space', his greens were certainly pure.
I think you, I and most UK greenskeepers are pretty much agreed we cant keep it out in our climate and demand for winter play, so live with a poa mix.
I think in some climates poa can be eliminated, but those climates need to be able to grow creeping bent or bermudas which with warmth will out perform poa. I suspect US supers will not keep fescues pure simply on the non aggressive basis of fescue.