For a start, it looks balanced (notice how the second channel is always the inverse of the first).
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.
It is a Async Serial signal.
Good guess, huh? Anyway you usually have some idea of what you are dealing with, and even if not, with experience you can usually pick patterns, as I did then. smiley