Hi there,
I’m starting this discussion to share with you our work regarding assets seized from mafia and criminals.
A single case should give the whole sense: we’ve found in France a villa seized from an italian criminal, but never really took. The villa has been for rent on AirBnb up to last year, despite the confiscation order.
A few more words would help to explain the main points:
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An evaluation would say us that we’ve 2 billion euros of confiscations a year through Italy, France, Spain, Germany and UK, that reach 4 Bln in watching all the 28 countries.
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Each country has data, but none published it in OpenData format. From UK probably has been released the best data thank to a FOI request. All data and reports we’ve gathered was collected here cb-eu/docs at gh-pages · ondata/cb-eu · GitHub
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Moreover, countries do not share data each other, despite a European directive on joint jurisdiction on confiscated goods.
You may find the whole investigation here http://eu.confiscatibene.it
and a brief description here http://journalismfund.eu/confiscatedgoods
Our aim is to share data and keep watched the phenomenon, so feel free to share your thoughts and reuse all contents, or anything else 
Thank you,
Andrea