What serial signalling format is this? (RS-485?)
The physical layer does indeed look like RS485, but that's just describing the differential voltage drive and idle-state of the lines. A peek at whatever's driving the bus in the source kit would tell you - it'll most likely be some standard 485/422 chip.

What the data format is is a different question, for that it's easier to look at the output from a 485 chip and trace the 0's and 1's. If you are sending some known data back &amp; forth then you should be able to determine that relationship pretty easily.

There may be some sort of messaging protocol above that, depending on the kit.