Hi Satya,
As far as I know, there is no link between the BoMs used for Risk and Compliance Management, and the BoPs used for Customs Management.
In Customs Management, you must either maintain the BoP (Component-to-Product relationship) in the GTS Product Master record, or set the ECPID record to indicate that an external BoM is being used. In the latter case, you then need to implement the BAdI to provide the components during the creation of the Export Declaration.
Hope that helps.
Regards,
Dave