C2/Mk2 I think was always just an "internet" name, the usual feature of this supposed variant are the turret addons, but those were supposed to be on all production Ariete since almost the start (it was discussed in a specialized magazine already in 1996), which is why all have the mounting points, those bolt looking things on the turret front. 200 of the turret front addons, named WAR, were bought but due to them not being up to specs (Protection? Weight?) the installation was cancelled and the contract was changed to reduce the price, same for the 30 side turret and hull addons, named PSO, the price was reduced for those too. The addons were still bought and are presumably in some warehouse. The WAR addons seem to be for KE protection, while the PSO addon seems to be intended for urban/asymmetric warfare.
This update is called either Ariete AMV or Ariete MLU, the first is the acronym for the Italian Aggiornamento Mezza Vita, which is the direct translation of MLU, Mid Life Update/Upgrade. AMV was in some budget documents, MLU is in these recent slides.
It's 3:30 am and my connection is unstable for some reason, I can post some of the documents and photos of the various addons tomorrow.