Bhaskar, First of all, we are not transferring material groups from ME. We have material groups which are created ME only and maintained under material group maintenance.
Having said that, I have researched little bit about this material group for you. IDOC field E1MARAM\MATKL has material group populated. ( basic data - material group ) .
And try mapping this field to WS node of
<me:ItemGroupRef>
<!--You may enter the following 2 items in any order-->
<!--Optional:-->
<me:SiteRef>
<me:Site>?</me:Site>
</me:SiteRef>
<me:ItemGroup languageCode="?">?</me:ItemGroup>
</me:ItemGroupRef>
of ItemCreateRequest_sync in XSLT.
It seems you need to change workflow items ( main split work flow xslt and other xslt's) and see if it works.
Thanks
Hari