I had a problem where if I left usecallerid=no in the zapata.conf file, Asterisk would miss the 1st 2 integration digits. Setting usecallerid=yes allowed it to work properly, although it still skipped it 1 in 20 calls.
I fixed it by turning usercallerid=yes, and adding the integration extensions without the initial # (as well as with the #), and telling Asterisk to ignore any stray, single #'s with a NoOp(). Now even though it typically misses the first pound, it still works fine. Luckily they're all still unique without it!
If anyone has questions on this, or would like help implementing this on a Partner II system, I can help. I did this same thing but on a smaller scale, so it may apply to a broader audience. Just contact me (Dan Polk) through my company - http://danpolk.googlepages.com