I'm expecting the ARC-170 to be the first and only 3-faction ship.
Being a relic of the Old Republic the Empire probably has a few mothballed Squadrons not yet converted to credits or scrap.
With the Empire moving to the TIE/Ln and being a bureaucracy probably sold stripped down obsolete military surplus. Ending up with PDFs and privateers across the galaxy.
And if it ended up in the hands of Scum chances are some when to the Rebel Scum.
So ya, first (and probably only) ship to belong to all 3 factions should it arrive.