If you don't have an MDI fitted, then it can't be the MDI loom that has been cut up and connected to the phone terminals.
Check and see exactly which terminals those wires would connect to when the quadlock is inserted to the rear of the RNS510 unit, and cross reference with the wiring diagram on the page I linked to earlier. From your picture it looks like they hit terminals 6, 11, and 10 on multi-pin connector number three. But if those pins are loose and can move about then they might've been inserted after the quadlock was connected, and could've been on different ones. Possibly the microphone connection? Take a look in the interior light in the headlining and see if there's a microphone in the slot there. That would be my guess, but it's a bodge job by someone so I'm not sure what you'll find connected to the other end.