The Uniden is a you say a proprietary system. To use NCS we must have the URL to each camera on the central system. Either http or rtsp URL.
Test and connect the UDW-155 module to the computer and add this USB module to NCS using the tab for Local Source / Webcam. If the driver is loaded correct and if you are lucky you should see it there. Sometimes the driver is for a 32-bit system so test also with NCS 32-bit version.
You can also use Wireshark and sniff the network how YAWCAM or Salsa communicates with the system. There you might find the correct URL´s.
Or as you say replace it with an IP camera and connect to NCS. That will probably save you a lot of time and frustation