If it was literally identical, you cannot do any more harm by 301-in the other 2 locations of that content into one canonical one. Perhaps identifying some really problematic URLs (destinations of bad links mostly) in the process and 410-ing those instead.
When you say "got smacked", all of them? That might be an indication of something other than duplication. If these three could be easily identified as one entity (by same AdSense or Analytics code for example), then they should have been able to pick one and make it canonical. It might not have been the one that YOU wanted but there would still be one site standing if duplication was the only issue.