The originURL is a convenience that allows you to use the same simple stream name on the edge as is being published on the origin it is pulling, but under the hood Wowza is putting it all together like this:
Using the streamName alias addon, or IMediaStreamNameAliasProvider2, or .stream files instead, you will want to use the whole rtmp url + stream name, which can reference any origin server. So just ignore originURL, don't use it.
So an edge stream alias file might have rules pointing to any number of different origin server streams:
In the above examples both origin streams are named myStream, but clients will subscribe to them from the edge as "stream1" and "stream2"
stream1 = rtmp://[wowza-address]:1935/liveorigin/myStream
stream2 = rtmp://[another-wowza-address]:1935/liveorigin/myStream