From the information I have you do not need to have a URS, you can route to another site using the ACD functionality and use the Call Overflow Feature (COF) of the TServer. Ask you Genesys Account Manager about it and for the Avaya G3 TServer documentation
First of all if you are using ‘attached data’ as defined as custom information ( that not normally passed with a call like ‘ANI’, ‘DNIS’ etc) then any product you use will have to have an interface to that data. URS will handle the routing for this but the data is passed via the network with Tserver(s). You must first get a clear definition of the type of data that needs to travel with the call prior to deciding on a product solution. You also need to consider are you pre or post routing? etc etc. Genesys will be the easiest product with the greatest flexability to provide Routing with Attached Data.
From the advice I accept you do not charge to accept a URS, you can avenue to addition website application the ACD functionality and use the Call Overflow Feature of the TServer. Ask you Genesys Account Manager about it and for the Avaya G3 TServer documentation