For a start, it looks balanced (notice how the second channel is always the inverse of the first).
So you can probably concentrate on one channel only. My initial guess would be to take RB1 and see if applying the "Async Serial" analyzer gives anything useful. Try setting it to "autobaud" and have it guess the baud rate. I'm suggestion RB1 because serial is "normally high" and goes low at the start of the byte, which is what RB1 is doing.