Hi
You could try something similar to what Bart suggested for searching metadata values that are not empty (
Matching stored search on any non-empty metadata value).
Create a new metadata field and pull the link values into the default value for this:
%asset_linking_info^as_xml^xpath:,://link_value%
The delimeter (",") could be whatever suits.
Then you should be able to search on that metadata field, or use a listing with conditions etc to get what you need.
Thanks
Peter