CUCM can only control phones and devices registered to it.
You can configure a location for the GW you use to connect to Nortel and that will avoid using more BW than necessary.
Simply configure a location A for GW and phones in location B.
The rerouting on Nortel... well, i guess you should be asking Nortel folks about that or refer to your Nortel documentation.
HTH
java
if this helps, please rate
HTH
java
if this helps, please rate