If the trunks are coming in via PRI then you will want to set the N1 or N2 fields in form 55 to 122 (cordless ext) for each DID. If they are regular CO lines then those would be set in form 14 (Non-dial in Trunks) on each individual trunk.

You may also want to look at all of the options in form 19 (Call Rerouting Table) for the N1 and N2 fields of the different items there. This form controls the Dial 0 and Priority Dial ) options, as well as some DID intercept routing and is set per tenant if you are using more than 1 tenant in your system.

Let us know how it turns out.

-Daniel