I am sure someone here can help you but...

I would tell them "We are using URC Total Control. I need a document that shows me addresses/ID's/Load names (whatever else) and a copy of the control protocol".

Once you have that you can move forward trying to figure out your end of it. If they cant provide that then IMO you need to talk with the client and explain that

A.You dont understand the system and cant reverse engineer their work for them

Or

B.You dont understand the system but you are willing to learn how to get their work done for them...provided that the client is willing to pay for your on-site education.

If you just jump into this you will end up miserable, working for free and end up with a client whos pissed off at you because you took too long and because its not working the way they expected etc etc. They will forget that you tried to do them a favor and it will all be your fault if it doesn't go smoothly.