Haven't tried it myself - and although it's aimed at the PSTN callers, the callback is being made from the gateway so your would think you could make it work; but maybe not.
But what is the business case here?
These are internal people on IP phones calling the contact center. If they have a DID it would work, but they would have to call out and in, not to an internal route point going to CVP.
Regards,
Geoff