I am not 100% sure that you are having a permissions issue, but it is
something to try out - set up a local developer database and give
yourself DBA permissions and see if you have the same issue or not.
If it is in fact the case that the problem is with permissions,
I'm not sure if there is a workaround or not. It might be that you
can instruct Liquibase to only work with the named schema, but I'm
not sure. The reason that Liquibase is requiring different permissions
than TOAD or sql developer is probably because they are either trying
to do fewer/different things, or they are just better at handling the problems.
If you can't get the necessary permissions, I would suggest
setting up a meeting with the appropriate managers to find out ways to
get the permissions needed. This may be a symptom of a larger problem
that requires changes in several different areas of the company.
Alternatively, ask the DBAs to give you a full dump of the schema
in SQL format, apply that to a developer database, and then use
Liquibase to generate the XML changelog from that.