Well, yeah, but it depends on how the service is set up.
When you migrate from copper to a T1, a lot of carriers will send the last 4 digits of the number called as DNIS, which is handled as if it were a DID. The customer may not even have a block of DID numbers as part of the package. So if they want the AA to answer the main number, you've go to direct the DNIS digits to the AA.