XCOM Transfer Control, referred to as XTC processing, allows interdependent transfers to be defined as a single group. Transfers in the same group can be held, purged, or released depending on the successful or unsuccessful completion of other transfers in the group.
Yes, the parameters have to be unique across different groups. All the XTC group JCL gets submitted to an XCOM server to process. The XTCNET and XTCJOB parameters must be unique across systems where the XCOM server can access jobs. When the combination is not unique, it may appear to work correctly, but you may also get unpredictable results, depending on timing.
For example, if you specify an XTC Purge Job (XTCERRPURGE), the CA XCOM server will purge all the jobs with the same XTCJOB name that are accessible on the system where it is running.
Even if the jobs run at totally different times, best practices dictate that they still be unique. The jobs might end up running at the same time due to unforeseen circumstances and cause problems in a production run.