Frankly Franko, they can't counter they argument that AOS is an abandoned work. There is no ownership claimed for this product until three years after the copyright holder was dissolved.
Bloodline's right. It's a tainted property and by all rights its copyrights should not be valid.
Copyright doesn't work like that. *IF* the rights were never legally transferred, they belong to Commodore's successors-in-interest, which would be either anyone Commodore owed money or Commodore's shareholders. Sorting out who would be difficult, and frankly the only way it would happen would be if Amiga Inc. sues someone and that someone challenges the legality of their ownership claims, or if a possible successor makes a claim.
However, any copying without a valid license is still copyright infringement - the only thing that changes is how likely it is you'll get sued. For trademarks the issue is murkier, as ownership of trademarks is at least in part defined by use and whether or not someone asserts ownership.
But honestly, at this point, who cares? The ROM's are easy to obtain, and we have AROS rapidly becoming a viable replacement on classics. And regardless of any rights granted or not to Hyperion, as long as no possible other owner challenges them, they're in the clear, and they do certainly own the rights to any parts *they* have developed unless they have signed contrracts to the contrary.
Unless you're planning on suing Cloanto or Hyperion, or want to try to challenge the Amiga trademark, whether or not Amiga Inc. owns the rights is pretty much irrelevant.