Stuart,
test-setuphealth cmdlet also does the readiness checks. So setup is not taking all the time just to check for updates on the internet.
If you want to update the ExBPA.PreReqs.XML file, before setup runs on a machine which does not have internet access then you need to replace the file under SetupServerRolesCommon<language>". Detailed instructions on this are located when we posted an article on this blog about updating the prereqs file when installing Exchange Server 2007 Service Pack 1 in a Single Labeled Domain environment. The blog article can be found at http://msexchangeteam.com/archive/2008/03/26/448511.aspx.
If you want the update the files on an already installed server which does not have internet access, you can copy over the files manually. After installation the files will be at <Exchange Server Installation folder>Bin<language>. E.g. D:Program FilesMicrosoftExchange ServerBinen. As a best practice do not overwrite the existing files, but make a backup of them. You can emulate what BPA does. The updater downloads the latest ExBPA.Config.XML from the Microsoft web site. It renames the existing ExBPA.Config.XML on the machine to ExBPA.Config.XML.<version number> (e.g. ExBPA.Config.XML.12.11.15.0). For the curious, the version number is located inside the XML file under the ConfigVersion key (E.g. ConfigVersion="12.11.15.0" for ExBPA.Config.XML).
Adam,
At this time we do not have any updates planned for E2K3.