Not sure how common they are in our zoos elefante, but that is what makes a zoo,a species that is relatively common on one Continent is rare as hens teeth on another such as koalas and some wallaby species most Australians wouldn't be botherd by them but the rest of the world is. I find it strange too when I see lists of exotics in other zoos and think how common they are here etc.
Here a list of Wapiti's kept in European zoos ( these are without subspecies-status ). There are also several zoos which keep subspecific groups : www.Zootierliste.de