That's a good question. It's something we haven't considered. We don't do ex post facto verification like the Auditor General does. She would probably be better able to answer that question than me.
On the other hand, federal programs, and this is in fact the case with our tax system, often rely on people's honour and good faith, and sometimes random, sometimes targeted audits are done. In the case of the article in La Presse, we can assume that checks to certify people's eligibility for this program are most likely rare and infrequent.