I think it's a issue with the centrex too. Let's bypass ARS 1st.
Set a dial out code for an ext. Go to extensions, dial out code, put an ext. # in, and put in the pool number you have the lines in. Go to that ext. now, dial the dial out code, then dial 9 (For centrex) and dial a number. See if you can get out then.
If you can it's a 2nd 9 issue, where you'll have to add digit in tables, ARS, Sub A, for local and LD.
KILLBOX