Hi,
From your description you are using a third party OPC server for the motion application. You could have a second Lookout process communicating with the same OPC server with no problems, as long as you do not exceed the number of I/O points your license supports.
Also, the process you are using for testing obviously could not overwrite datamembers (or registers if you will) that would interfere in the overall application, in other words you can test your application as long as you keep the coherency of the test.
So the answer would be, yes it is possible, however you are still limited to the number of I/O's your license supports... You may even consider upgrade the number of I/O's you have in your license.
Best Regards
Andre Oliveira