Ok, after my final investigations, it seems problem with the escape of "@" which is changed to DOMAIN"\"User. Everything else is the same. Only, only pulseaudio ssh forward doesn't happen. I have found this inside /var/log/syslog:

Dec 14 16:01:43 bgtrmx02 pulseaudio[11757]: pid.c: Failed to open PID file '/home/likewise-open/DOMAIN/iboyadzi/.pulse/512381a4f3b57a9260ac14f100000005-runtime/pid': No such file or directory
Dec 14 16:01:43 bgtrmx02 pulseaudio[11757]: pid.c: Failed to open PID file '/home/likewise-open/DOMAIN/iboyadzi/.pulse/512381a4f3b57a9260ac14f100000005-runtime/pid': No such file or directory

- I've compared 2 newly created user folders (local and LDAP). There had differences:
 * media symlink to /tmp/DOMAIN\USER_media wasn't successful for LDAP user
 * LDAP user has .pulse folder with the pid error above
 * local user has .pulse-client.conf and .pulse-cookie inside ~/.x2go/C-Username...dp32/
 
- ps axwww compare showed no difference

The point with LDAP user logged in locally, has same effect as changing /dev/snd/* files permissions to 0666 (SUBSYSTEM=="sound", MODE="0666" part), and thus the sound is hearing on the server side.

My questions:
1. Do you know how this SSH Pulseaudio forwarding is implemented. I would like to try to create manually a new pulseaudio forwarding to current remote LDAP account session.
2. Can you show me where in the sources, are the parts written both for the server and client side. When I get more deep understanding how this pulseaudio is happening I would provide exact reason why it fails.

Thanks and Best Regards
Ivan