Thank you for your replies! Luckily for me in this case, the trunk line I wish to access connects to a code call system. So there is no risk of toll fraud, only mischievous code calling : ) But I can password the code call system if I need to. Have been scouring the docs and havent found a lot of info on DNIS and how I could get that to work for me. Looking at DISA it appears there would be short period of time with a dial tone before the auto attendant picks up and I'm not sure that would be desirable. I was hoping there was a way to directly access the trunk line from the auto attendant but not seeing any documentation on that. Though I do see some mailboxes transfer to numbers that have special characters in them...
I did try adding an extension to the auto attending who's only purpose was to be permanently forwarded to the trunk line, but for whatever reason the code call could not detect DTMF through the patch.