I just spent the last few hours going through how these are supposed to work in order to use them with an emulator. From what I understand, there's supposed to be a primary file type that you extract when looking through these archives (I refer to them as such since none of them have been a single file by any stretch) and then refer the emulator to when you have it load the cdvd.
To be clear about what I've been looking at, the two iso files I've looked through have been very similar, so I'll talk about them together. They each have one rpk.bin and a system.cnf file, then a SLUS_211.13 in one and a SLUS_217.35 in the other. There are then several folders filled with .vp, .sif, .pcm, .pss, .irx files, and one .img file in each of them. I've extracted all of this into a folder and referred pcsx2 to the bin file, which results in something like this:
Image type = Audio CD
* CDVD Disk Open: DVD, Single layer or unknown:
* * Track 1: Data (Mode 1) (308976 sectors)
Closing plugins...
Closing SPU2
File not found.
Path: IsoFileSystem
(pxActionEvent) IsoFS could not find the root directory on the ISO image.(thread:EE Core)
Closing PAD
Closing GS
Plugins closed successfully.
Shutting down plugins...
Plugins shutdown successfully.
I've also attempted to compress these files together and rename the result into .iso (since the original files are extracted from a .iso file anyway) but that gives me the same response in the log. I'm at a complete loss at this point.