Once upon a time about 20 yrs ago, a customer of mine with a large call center, modified their phones (Nortel 2216 ACD phones) with a voice recorder/playback card so when they'd answer a call, they'd press a button which would announce whatever they pre-recorded by hitting another button on the phone. Of course this was all 3rd party hack job stuff that voided the warranties on the phones - but it worked.
I suppose you can do something like this with an analog phone and a device such as a Viking EV-1 or similar - perhaps something that goes between a handset and IP phone if you don't have analog ports on your system. Google around - there's solutions out there.
But no, what you want to do is not possible with a Nortel PBX and CallPilot for outbound calls (it will with inbound). You'll need a third-party product to achieve your goal.