An spsbackup effectively just calls SQL client tools to backup each of
the individual databases. In your backup folder you will see a file for
the _Sites, _Prof & _SERV dbs. These are just SQL backups of the
original databases and can be restored to any SQL server.
So I'm suggesting that you could take the _Sites backup and restore it
to a SQL instance somewhere. Once this is done you would then have a
couple of options. First there are some community tools out there that
allow you to navigate databases without even attaching them to a WSS/SPS
instance.
The second option is to attach the database to an IIS virtual server
that has been extended with WSS. However this would HAVE to be on a
separate physical server (standalone or different farm) to the one where
the backup was taken. The reason here is that if you import a content
database that has the same entries in the Sites table as an existing
database that is already attached then the existing sites will be
repointed at the newly attached database. This happens due to the fact
that there is a master Sites table held in the configuration database
that lets SharePoint know which content database to go to to get the
site content. Once the database is connected to a WSS instance then you
can use stsadm to backup the desired site and then restore it into your
operational portal site.
Hopefully the above explains enough for you to move forwards. Note the
above is all theory on my part since I have never actually tried
this!!!!