Hi Moazzam Mubarak,
Cross company document will be created and document gets posted in the other group company only if you specify the other company code in the line item of the journal. Then only cross company code document gets posted and relevant journal entry per your settings of OBYA will get posted in the other group company.
If you just specify the customer / vendor (referring to group company) in debit line item and credit the revenue account, it will get posted only in your posting company code. It will not get posted automatically in the other trading company.
Regards,
Sridhar