I'm not sure if it's under the 3yr/36K or the 5yr/60K powertrain warranty. All I know is that my friend took his car (with a failed 96 Legacy OB left rear wheel bearing) to the dealer and the dealer repaired it under warranty. And this at 59K miles and 1 month left on the PT warranty. That leads me to believe that it "is" part of the PT warranty covered items.
Worth a check.