To trigger a batch job, you need to have a trigger monitor program running. This is a long-running program which examines the trigger queue to determine what job needs to be triggered for what queue and submits relevant job accordingly. How you implement this depends on your requirements. Typically, you would deploy a trigger monitor program as a generalised utility program so that many could use it.
When a trigger message is placed on Init Queue, a trigger event is created for eg on every first message. When a trigger event is occured, a transaction can be trigger. Now transaction is running under CICS, so you can create a Internal reader TDQ and write the batch job to it.
This is done thru CICS Adapter.