Because single line extensions (including voice mail ports) cannot flash to the CO line, you can directly do a Centrex transfer (flash, pause, number, pause, disconnect)
However, you CAN use Centrex Forwarding on a phantom extension, and transfer the caller to that extension. The key is that the call has to come INTO the system on a Centrex trunk.
Forward the extension to *-pause (hold)-telephone number-#
And this assumes that you have a Magix with the Merlin Messaging installed in it.