Here is the roster of the NY159th Infantry where you can find most of the names mentioned in the Picayune article. There is mention of a Brian Hopkins (p.51) being sentenced to life imprisonment at Tortuga, but no mention of his sentence being revoked and Brian Hopkins is mustered out in Oct. 1865 with the rest of the regiment.
Don't know if that helps your research or not but the NY 159th roster corroborates the Picayune article to some degree. It doesn't look like any of the culprits served their sentences either.
Some states apparently had difficulty enlisting enough men to meet their quota even with the bounty they offered to those who enlisted. I am reminded of an ad seeking enrollees in Mississippi to meet the Massachusetts quota. The ad originally appeared in the Vicksburg Herald newspaper. The date of the ad was not mentioned when it was reported later in the April 4, 1865, Galveston Daily News, which was where I found it. The italics, caps, and spacing below are as printed in the Galveston paper:
RECRUITS FOR MASSACHUSETTS QUOTA!
$625.00 Bounty
$425.00 CASH DOWN
The same bounty and pay to
WHITE OR COLORED RECRUITS.
All get sixteen dollars per month.
Choose your own Regiment or Company.
Liberal pay to agents for bringing recruits to me.
Lieut. Col. E. C. Kinsley,
Ass't Provost Marshall of Massachusetts for the District of Mississippi
Headquarters at Vicksburg -- Office on Washington Street near Clay, over Col. Saunders & Co.'s store.
The bounty was equivalent to 39 months of pay and was probably a big incentive for newly freed slaves in Mississippi, who doubtless didn't have great prospects for earning much money otherwise.
Lincoln had issued a call for three-year enlistments on May 3, 1861 [Source: Link], and many of the thousands who enlisted in response to his call might choose to leave the Army and not reenlist when their three year period was up in May or June of 1864. The Provost Court sentenced the men from the 159th in March 1864. The Army might have thought it in their best interest to retain all the soldiers they could, including in this case, convicted rapists, to offset the men who might leave at the end of their three-year enlistment.