I've heard of one water in Butler Co holding wild brook trout in catchable numbers but have never fished it myself. The PFBC has a bunch of different kinds of lists you can find on their website, including one with waters in which they've found natural reproduction of trout in each county and also streams with different designations that tell you what the wild trout quality is like. I was kinda surprised at all the places they found natural repro in Butler County. Keep in mind that's not high numbers or reproduction on a level that will sustain a fishery, but just places they've found it to be happening.
I don't fish it often, but the DHALO area of Buffalo Crick on the Butler/Armstrong should be getting stocked pretty soon and doesn't close for business on March 1 like most other trout waters around here.