All of the unica saddles I've ever seen had solid round steel rails. The round rails were zinc or cadmium plated. They may appear to be alloy in digital photos. I've seen photos of models made specifically to work with a unica post and those rectangular section shaped rails appear to be steel, too.
I don't think a specific "pista model" was created. Cinelli did offer entry level models. Track bike often used these simple saddles. The events were generally too short to matter much.
Also, all of the unicas I've seen, except for one, did not have the ability to adjust the tension. The Cinelli catalogs I've seen show only nose detail of models that are adjustable.
I acquired a Jeunet that had a uncovered unica nitor saddle without tensioner. I later found a specification for the bike that provided evidence that the saddle was orginal equipment.
Todd Teachout
Hercules, CA