Yes, it does support what you are asking. Any T1/E1 VWIC that comes with the UC500 supports both CAS and CCS T1's. The CCS T1 (PRI) has a separate channel which is used for signaling and the "DNIS" digits you are reffering to are sent over that D channel to the UC500.
DNIS digits are the numbers that someone dialed to reach your company. Since the phone company is sending you those digits, you can route calls in your company according to what the person on the far end dialed. With POTS lines, the physical line is associated with the number. Since a PRI is one physical line, the phone company as a service gives you the option to digitally (D Channel) see what number someone dialed to reach you.
When you have 20+ numbers (718) EEE - XXXX. The "EEE"s (Exchange code) usually stays the same and the XXXX's (Subscriber number) can differ. When the phone company asks you how many DNIS digits to send, people usually say four because the exchange is always the same. If exchange is different you can ask them to send five or more digits instead of four. Five or more isn't always the necessary because the last four don't always overlap.
With CCA, you have the option under the direct inward dial tab to route calls based on that four digit number.
