Well as of R16 Joe I know that the CCRS isn't the way to do it. It does become possible in R16 though to disable the ability for the user to press 0 to exit the queue, and I think separately control where they end up if they do.

So the question is then how can you find out... I suspect that both the CDRs and XSI-Events for the queue will reflect a redirection cause. In the CDRs you will find what you are looking for in RedirectingReason and serviceExtension fields (see BW-AccountingCDR-InterfaceSpec-Rxx.x.pdf)

In XSI events there are similar diverted events. On the queue number there are a limited number of ways for a call to be diverted post answer - either distributed to an agent, overflow on time, overflow on stranded (all agents joined to the queue log out) or escape on user pressing a digit. There are a few more reasons for divert pre-answer, but they can disambiguated.

ROger.