“As you mentioned, it does consume network bandwidth. However, if you had access to the server where those repositories are hosted, you may run it via
file:// protocol. It is proved to be faster and not network consuming.
svn propget svn:externals -R file:///path/to/repo/Branch
Also, if you had the entire working copy in place, you may also run it within your WC.
svn propget svn:externals -R /path/to/WC
Hope it helps you to achieve the results faster!.”