This thread seems to be the original source for the Junker Blues/Angola/prison song connection. I can't find anything else to back PoppaGator's version of events.
Tis curious, don't know about Louisiana but, processing junco or jonque into finished “oakum,” as the Anglos call it, was traditional prison labor akin to treadmills and 'making little ones out of big ones' &c. Out of fashion by the time this song was written but not for any of the supposed precursors should they ever pan out.
Here is Junker Blues & Fat Man together. My ears don't hear a musical connection to Dr. John et al but that's just me.