I find it "interesting" that they would leave that so prominently displayed on the trunk.
The TZ3 (Corsa and Stradale) are cars developed by Zagato using the ACR as the starting point. They have a carbon fiber tub mated to a steel chassis, dressed with hand formed aluminum panels.
Here is a link to the cars
http://www.autoblog....stradale-zagato
As for sharing and development, I would think that the performance brands of FIAT-Chrysler (barred Ferrari) will have both a hand in the development and a go at creating their own version of any platform and architecture that we'll see coming out. And yes, reportedly Maserati guys have been seen stateside, and "Viper" mules have been spotted testing in Italy.