Clearly, they haven't been phased out since they are still present at a number of zoos. I'm assuming you're asking if the AZA has recommended a phase-out or not. Remember, the AZA can only recommend a species to be phased out because, in the end, individual zoos have all the power regarding what species they want to keep and which they want to send away. For example, Bronx and both SDZ Safari Park have been known to keep various ungulates that the AZA recommended for phase-out.
To answer your question, everything ungulate related can be found at this
site, if you go through the various documents it'll tell you whether a species is managed as a Green, Yellow, or Red SSP, or is being phased out. But as Thylo said, they are not recommended to be phased out, they are currently managed as a Red SSP.
Are they a Yellow SSP now? It says
here that they are a Red SSP. The population is doing rather well with a few facilities like CCTU breeding them really well but there aren't very many holders atm. I know SDZ Safari Park is interested in acquiring the species, do you know of any other zoos interested?