If you’re using Connection 7.x you could get close to this without too much effort using the “route from next” functionality.  You’d create a routing rule for all forwarded calls that would send it to a call handler that plays a greeting “Hello, you have called company XYZ” and that have an after greeting action of “route from next” – which would then process the call as normal with the next routing rule – by default the “attempt forward to greeting” which would then find the forwarding number and go to that subscriber’s greeting.  If it was set to system it’d sound something like “The user you are trying to reach is on the phone or not available…”

This would provide about the same message you want with the creation of a single routing rule and call handler – all forwarded calls coming into the system would hear that first “hello, you’ve called company xyz” so if it was forwarding from a non subscribers phone and going to the opening greeting you’d want to take that into account and not repeat it for that greeting – but other than that it’s pretty straight forward.  Direct calls into the system wouldn’t hear that so folks calling into check messages would behave as normal.