I guess I don't see why the fact that someone just recorded that audio straight into the phone from the video means its fake.
It seems like vic on the other end was just a mcguffin, I immediately thought "oh ok, there was an rvb reference to signify it's legit and halo related" nothing more.
I didn't try anything with the menu navigation, maybe entering it codes when you call will open up some new voice message/mailbox? Hey, what if that's it!
I think a good way to get the audio would be to call on skype and record it with audicity or whatever that open source audio application is.
It's pretty cool, I saw this this morning and got nostalgic for ILB so now I'm listening to ILB and thinking about this new ARG.

"someday! EVERYONE will cut their chickens like this!" ROFL