PRS has indeed changed the flavor of them from year to year. They also vary from model to model. I don't know what type of magnets they are as in materials, but they are blade magnets. Unlike other pick ups, they have no bobbins. The wire is directly wound on the magnet in a proprietary process developed by Winn.
Where the 513, 305, DC3, and Brent Mason all vary by number of winds, the 509's are even stranger. Each pair of singlecoils is the equivalent of an asymmetrical humbucker being that one has more winds than the other. Only the one with more winds is tapped like a 408. I also could swear the 509's use different wire as they have a clarity and articulation that is closer to 1957/2008's than the more McCarty like 513 pick ups.
There is a rumor floating around that 513 pick ups are descendant from bass pick ups, because they look similar to the Gary Grainger pick ups. But, Gary Grainger's for the most part aren't tapped except in some of the Private Stock models.