Yea, I poked around the Internet Archive quite a bit, but didn't find anything regarding the MX1090 at all other than sales literature.
I know the com ports are 4 wire....+Vdc, RX, TX and ground, and it appears to be a standard 2.5mm 4 conductor plug. It receives power through the com ports, which if you have it connected from an XRX, receives power from the DB9 on the XRX (which powers a BT module if you have one for the XRX).
Input from the XRX goes to Com 2, along with power/ground. I also want to say that Garmin format traffic data is output through Com 2, and standard format traffic output is from Com 1, but that's unsubstantiated at this point.
I would throw it on the computer's serial port to know for sure. I'll figure it out eventually with a logic probe, but the manual/pin outs make it easier. A couple of bare wire connectors (PN# MX1090-CBL4) sitting in someone's clearance bin would make things really easy....
Someone HAS to have a manual for this thing somewhere....