Писать свой загрузчик метаданных.
If you have metadata that was created outside of ArcCatalog, you can import it if it’s stored in one of the input formats supported by the
< id=glossary_federal_geographic__committee_fgdc2723 height=0 width=0 id=clsid:adb880a6-d8ff-11cf-9377-00aa003b7a11 name="WH glossary popup">< NAME="Width" VALUE="26">< NAME="Height" VALUE="26">< NAME="Command" VALUE=""></>'s metadata parser utility, mp—these are the FGDC CSDGM TXT, FGDC CSDGM XML, and FGDC CSDGM SGML formats. ArcCatalog uses mp itself to import and export metadata in its supported formats; mp is not an ESRI utility.
Т.е. если Ваши метаданные написаны в формате, понятном утилите mp, то они будут импортироваться. В противном случае нет.