Yep, that was one of the problems. My dialplan already has two 00, adding a third one screws up. I'm sure I can make it work somehow, but then there where other problems (test call does not work, MOH does not work) so when the Zentyal staff told us about a reworked Asterisk in Zentyal 2.2, I figured it just wasn't worth the trouble.
Getting my 4 pap2T's to work with Zentyal is an absolute priority, together with several sip trunks. I've been fairly active in the voip field the last years, its a dream to tailor custom dialplans and use sip trunks based on destination.
I hope the Asterisk implementation will allow that, it it needs being hacking into that's no problem. On 2.2, that is.
Cheers.