There is a lot of conflicting information.
In pet food, it seems to be an concentrated extract from Yucca Schigdera species. Supposedly to control urine odour and the saponin in it also may have anti-inflammatory benefits. Some other health claims (GI health, bone health, Immune support) though I do not know if that is for people, animals or both…
I also read this:
The stems or trunks of yucca store carbohydrates in chemicals called saponins, which are toxic, not to mention taste of soap. To render them edible, the saponins need to be broken down by baking or boiling.
http://www.gardeningknowhow.com/ornamental/foliage/yucca/yucca-plant-as-food.htm
This may be why the chews you see for small animals and birds are thought safe, because it is dried yucca? I couldn’t tell you if those products are naturally dried or processed at a certain temperature.
Sorry if my post has created more questions for you. I don’t know what you’d have to do to deem parts of a house plant safe and personally, would avoid feeding it. As for hair balls, rabbits really shouldn’t get these with the correct diet. A plentiful supply of hay and water are the best for moving hair through their GI tract.
There is a section here about hairballs (under the 3rd heading). http://www.bio.miami.edu/hare/ileus.html