Ice Cold Killa is fairly unique in that CJ enters the Pleasure Domes through one enex and exits through another. I guess something similar happens during Just Business as CJ passes through the Atrium, but then he's usually locked into an escape mission. Perhaps observations during a Nebula collection (see special vehicle topic) might provide more clues. Or not, the enexes are different and may provide different results.
So my best guess is that the rare dealer is spawning because of something to do with enex path, but that's still just a guess. At what point in the mission did were these images taken?
Off topic: If you want to see a screwed up enex try exiting the Pleasure Domes using the same rooftop entrance used to enter.
The Biker and Hispanic dealer shown above are mostly functional (on PS2 and PC, not verified on systems) if the zone properties are tweaked a little. In a normal game the biker dealer will spawn readily in SF if Ballas, Vagos or Grove density is glitched into the zone - easy on PS2v1 using the fly off the map trick. The biker dealer is frequently seen near CJ's starting point on a brand new game. Otherwise I've never seen him outside of SF.
The Hispanic dealer is a bit more difficult to spawn. He's appear in some LV zones without too much effort, but for a lot of zone types the ped type variable needs to be adjusted or he won't spawn. And if you fiddle with the ped type properties he'll appear in country and, iirc, even LS zones.
I never gained full control of the dealers, but by experimenting enough I manage to implement both the Hispanic and biker dealers on a normal game simply by adjusting the zone properties in the save. Check out the Chain Game save linked in the mission help subforum if you are curious.