In the 1990s a fleet of reefers emerged that used cryo-CO2 to cool it’s perishable loads instead of mechanical refrigeration. A company called Cryotrains operated these 70' reefers, and Walthers had an HO model in kit form that’s been discontinued for quite awhile.
http://www.railcarphotos.com/PhotoDetails.php?PhotoID=5516
Were cyro-reefers the modern reintroduction of the ice reefer? Of course it looks like Cyrotrains reefers have been converted to mechanical refrigeration judging by the outside refrigeration unit in recent photos of these cars.
http://www.railcarphotos.com/PhotoDetails.php?PhotoID=31789
ARMN and other current reefer fleets are mechanical too, so it sounds like cryo-refrigeration didn't catch on very well.