Let me preface this by saying I'm not a developer and I don't know
much about these things.
That said, I believe that information is proprietary. I've never heard
of them or anyone else publishing such a list. Apple's probably comes
from a variety of sources -- they've been making Chinese input methods
since the 1980s, after all. If you are a developer you can license
data like that, but the people who own it keep a pretty tight grip on
it. Google got in trouble for stealing someone else's data when they
first launched their input method. It goes way beyond any one
dictionary, I think.
Eric