I am going to say this as far as Dban you can recover data but the data you recover would not be usefull to any one short of a technophile that specilizes in data recovery for data farming. You got bits of info that are left but at a trace amount if that, in order to string the data to anything revelent usage for any purpose one must spend 3 to 12 days depending on what you are trying to piece together..
I know for a fact that items can be recovered.. I expermited with a jpg picture on a 20Gig hdd and all I was able to recover was one small section of the photo in full and reconstruct it even then you can tell I had missplaced data but the geist of it was clear.. if you have nothing else to do and you are consumed with the ""information " you want then some one could spend week, Months, Years even recovering any thing revelent to use.....
Most above average data recoverers that are in to data farming will bypass a drive that has been whiped or blank making a one run using free or open source data recovery to try to gather info preferring to go the easier route a HDD that is known to have info on it that will provide more usefull with quicker results, IE 2 to 4 hours of searching vs days, weeks, months, years to recover a Dban quick wipe...........
I know of four orginizations that can recover data form a full nuke of Dban, 1) NSA 2) CIA 3)MIT 4) Bill Gates........
if they would even try to recover data it must be national security or apple secreats..........