Most likely, the downdraft will be flush against the back of the cabinet so it may not be possible to "invade" that space. Even if you can, it may not be a good idea. The refrigerator will put out heat that could cause problems for the cooktop, and the cooktop heat could cause problems for the wine fridge. I would try to find a different location for the wine fridge.

I agree, it doesn't seem like that would work, assuming the cooktop/downdraft are also spec'd for a 24" depth and would take up the whole thing.

Even if it doesn't, I also agree on the heat output issue, and second the motion for relocation.

You should be able to find the installation specs for the cooktop online that say what can be in the cabinet under it. I would bet that in order to keep the cabinet under the cooktop usable, even to allow drawers, that the downvent is flush against the back of the cabinet.

Even though it won't fit I don't think heat will be a serious issue. Cabinet-install fridges all vent to the front and the down-vent from the cooktop won't get all that hot, and is only run for relatively brief periods of time.