After some hours of late night hacking I’m finally running an Ubuntu 9.10 with Asterisk, Freepbx and my HFC ISDN cards. I took a long time to figure out, how to get the ISDN cards running with dahdi instead of misdn. But now it is working.
It is a steep learning curve from asterisk 1.2 to 1.6, oh yes. But it is worth the effort.