Hi Surya,
If you use a single Operative COA for all company codes, then you do not need Group Chart of accounts, as both the company codes would be posting in the same Communication expenses GL and would not be posting in different expense GL's.
In this case, you do not need Group chart of accounts for consolidation.
Refer our last discussion on country chart of accounts, in that any local requirement is met through Country chart of accounts but the posting goes in same Gl across the globe.
Regards,
Kavita