Either way, the cut-off (as good as it is or isn't) will likely not be maintained with HIDs. The cut-off is designed to control the light from a halogen source. An HID source is a different animal. The filament is not in the same shape and is likely not in the same location with most re-based HID bulbs (to fit into an H8 housing).
Here's a great example, from a Hyundai Genesis forum thread specifically discussing the hazards of installing HIDs in fog lamps:
Gencoupe.com thread
Towards the bottom, someone shows a picture of an HID fog lamp conversion in a Corvette. Note the well-controlled optics on the left from the proper halogen bulb. Note the vast amount of scattered light from the HID bulb in the right side unit. No offense to Cruze owners, but I wouldn't expect a Cruze fog lamp housing to have any better control over an HID retrofit than a Corvette fog lamp housing.
Maybe you can put an HID kit into a Hyundai and it works, I don't know. The only way I would recommend doing what you're doing is if you swapped some projector fog lamps in, like say from a Ford Fusion. Projector housings, by their very nature, tend to give better results with HID retrofit kits than do multi-reflector housings. But even with projectors, you still have to be careful. Here's an example of someone with an MDX just like mine, who put HIDs into the halogen projector housings. Look at all the waste glare, and the intense light above the cut-off from the squirrel spotters:
MDXers.org thread
HIDs really need housings designed for HIDs. It hardly ever works right in halogen multi-reflector housings, and even halogen projector housings are a roll of the dice. Sometimes it works pretty good and sometimes it doesn't. Even when everyone's using the same housing (as in the MDXers.org thread), some apparently have better results than others depending on the exact kit they're using, which is more evidence that filament placement on this re-based HID bulbs is not all that precise (meaning you're likely to have poor results in a halogen multi-reflector housing).
Edit: if these really are the OEM Cruze fog lamp assemblies as the auction claims, I would absolutely NOT recommend an HID conversion. The housings do not have a physical shield covering the front of the bulb, requiring the bulb to have its own shielding. I have seen a few HID kits which supposedly come with self-shielding bulbs, but I have not heard good things about them.
eBay link
Your comment about the main head lamps having a better cut-off than the fog lamps seems to correlate with what appear to be the OEM fog lamps in that eBay link. There's only so much you can do with the optics of the lamp housing without a bulb shield. My Dakota had very similar fog lamps: it took an 893 bulb in a 3" or 4" round housing. The bulb had a painted tip, which was the only shielding in that design. My '01 Cadillac STS was similar; it took a painted-tipped 880 in a rectangular housing. By comparison, Japanese and European fog lamps tend to have better optics. My Corolla (see earlier photo, with the OEM assembly on the right and an aftermarket assembly on the left) and MDX both had/have fog lamps, and both housings use physical bulb shields to better control the optics from the 9006/HB4 bulbs in the housings. They give good output from the 55W/1,000 lumen bulbs and a good light distribution with an excellent cut-off.