Yes, both voice names and greetings are strored in the \commserver\streamfiles directory - however remember that voice names are also synced to the directory so if you just change/remove the WAV file on the hard drive it'll come back again with the next sync.
The naming convention uses the alias of the primary call handler associated with the subscriber. So if the subscriber has an alaias of jsmith the standard greeting wav file name will be:
ch_jsmith(bunch of spaces)_Standard_MrGreeting_xxxxx.wav
where xxx is the system ID of the Unity server in hex (something like 0da673d5). And the spaces are going to throw you off... not sure why they opted to do that or if someone just wanted all the file names to be the same length or appended when they shouldn't have or something... it's not considered a bug but it is kinda goofy looking. You'll see something like 30 spaces in there so the final file name will look something like this:
"ch_jsmith Standard_MrGreeting_0da673d5.wav"
All the greetings will follow that same convetion, just the name in front of MrGreeting would be different: standard, internal, busy, alternate, off hours.
voice names are better formed and would look like this:
"jsmith_SubName_0da673d5.wav"
