P.S. Are someone going to implement
     <interface type='bridge'>
        ...
         <source bridge="...">
        ...
      </interface>
part of openvz driver? :)
I plan to implement it in a month.
It will be fine if you are ready to develop the feature.
 
How we can save, say, a name of a bridge to connect to?
óan we save and use for that purpose an xml description
of domain, say, /etc/libvirt/openvz/<veid>.xml?
Or, more precisely, for which purposes we can use an xml
description of an openvz domain? (I think, that, in general,
libvirt must use /vz/conf/$veid.conf, and appeal to
/etc/libvirt/openvz/<veid>.xml only in special cases, like
described before.)