The official name for an Area Code is Numbering Plan Area or NPA, and for Central Office Code is NXX (prefix or exchange code), refering to the digits N = 2 thru 9, X = 1 thru 0. If you want to find out more visit NANPA's website nanpa.com NANPA is North American Numbering Plan Administration.
Going back to the question at hand, if your DID numbers for 272 and 292 come in on different PRIs that may work by setting up each PRI accordingly to send number by station. I have never tried it this way, because all the Legend/Magix I have worked on have only one PRI. So you will have to experiment with the PRIs to see what the limitations are with multiple PRIs on the switch.
Are the DID numbers for 272 coming in on one PRI and the 292s on the other? Or are they all coming in on both PRIs?
How Telco routes the DID numbers will make a difference. You will want them as separate Trunk Groups in the CO switch, which means your PRIs will be separate from that side of the facility.
One point of information, the term "ported" or "porting" only refers to telephone numbers that are using Local Number Portability or LNP, when you change service providers or switches and take your numbers with you, not when routing DID numbers to a facility, like PRI or on DS1.
By the way, if your service provider is the current AT&T footprint, they are not restricting numbers to send on PRIMARY ISDN.
....JIM....