Just had a quick look at the first few chapters of Abyss
and the Section 31 guy makes a mention of "former Cardassian holdings" and Bashir corrects him, calling them "protectorates" set up by the Feds, Klings and Roms to protect Cardassian territory until the Cardassians can resume control.
Had a look over at MemoryBeta to see what they had from the non-canon sources and was surprised that they only had a little bit. Thought they would have more from the DS9 relaunch but only Stitch in Time
gets a mention in their article on Cardassian history.