G59P offsets are for moving the coordinates to a different reference. However, this would not make a good choice in my mind for cutter wear compensation as it shifts all x y values the same amount. So for example, you're cutting a piece on the low X or Y side of the part and your offset is adjust for a .002" wear on the tool, then cuts on the high X or Y side of the part would be even further off by an additional .002".
As I understand it, you would just adjust your tool radius in the tool table to allow for the wear on the tool. Then your normal tool compensation would take this into account and be correct all the way around the part.
Take this with a grain of salt, though. My knowledge on this is somewhat limited as I'm relatively new to milling and do not use tool compensation as my CAM software does this for me. Of course I have to make sure the tool tables in THAT software are accurate, but either way it seems that the tables are the secret to mastering compensation values.
Stephen "Highspeed" Kruse