Hi @SachinDhir,
As far as I know unless otherwise, you add the assets from the Assets Library to other Adobe solutions (Ex. ACS) you won't get the URL. Even if we get the assets added from the Assets Library to ACS deliveries/landing pages, the URL reference that you get for the asset will not be able to distinguish (Except the unique number given for each asset) from other assets loaded locally.
One thought: If it helps, try to export all the delivery templates as a package and open the XML to get the asset URL.
Let's see if anyone else has any other thoughts.
Thanks, Sathees