Back when I was planning our Sept 2007 trip, the disneyland site clearly stated that PPH and DLH guests could use each other's pool, but they couldn't use the GCH pool.
And my stepmom, who had stayed at PPH several times, stated that they often used the DLH pool.
But at some point before our '07 trip, that wording disappeared from the disneyland website, and it's now a policy that you can only use your pool (unless your pool is closed entirely and they tell you otherwise).