Then description on how to set it up http://support.microsoft.com/kb/972721/
Please remember you must restart the server for the fix/setting to be applied.
Adam has a blog on what is showing in the toast/popup.
I ran in to some minor issues due to the fact that this fix must be applied “Download the UcmaRedist.msp package now” (http://support.microsoft.com/kb/970679/) my experience is that this fix isn’t applied if using Microsoft autoupdate.
On Cisco CUCM device->phone->Line”X” setting, it’s the “ASCII Display (internal Caller ID)” that OCS show in the popup/toast
In Exchange 2007 UM if you get Missed call og Voicemail notification mail, it’s still the phone number, so no Displayname without your create contact with that phone number, more information in this blog.