I've had mixed success having VSE 8.5i uninstall Symantec. Symantec 9 seems to uninstall cleanly but we've had some Symantec 10 machines that have required an exorcism of the software.
The VSE 8.5i installer simply makes an API call to the Symantec uninstall routine so if Symantec doesn't want to uninstall you're stuck visiting the machine. The VSE 8.5i installer does know how to trigger the uninstall without requiring a password.
There's a NONAV utility out there that's available through Symantec that takes a more brute-force approach to uninstall by manually stopping services, removing DLLs, registry entries, etc. This was a very valuable part of our toolkit during the migration.