Hum... I've searched the study, and it looks like results are still scheduled to be published this year. Granted that it was a quick search, but I get no source for the claim that the result was negative.
Besides, UBI being cheaper to administer than current social security, failure in finding any difference is a reason to adopt it, not to keep the status quo.
UBI is definitely not cheaper that current social security. "To administer" maybe, but the total cost is probably orders of magnitude more, and doesn't even solve the problem: certain demographics will still need extra.
I don't have other sources at hand - just memories from when the study was published and there was quite a lot of discussion.