I believe there is another back-door for getting this information inside AutoCAD. Like with the Inventor add-in, there is no official support for this technique.
If you use the following code from your add-in, you should be able to get the userId and ticket of the current Vault session.
if (VaultExplorerAppBase.Instance == null)
{
throw new ApplicationException("Unable to get Vault connection");
}
VaultConnectionManager connectionMgr = VaultExplorerAppBase.Instance.VaultManager;
if (connectionMgr.Connection.IsSignedIn() == false)
{
throw new ApplicationException("Vault connection doesn't exist.");
}
IWebServiceCredentials credentials = new UserIdTicketCredentials(connectionMgr.Connection.SecurityContext.RemoteHost,
connectionMgr.Connection.SecurityContext.KnowledgeVault,
connectionMgr.Connection.SecurityContext.UserID,
connectionMgr.Connection.SecurityContext.Ticket);
It has dependency on following dlls (which are located in AutoCAD installation directory). None of these DLLs are part of the supported Vault API.
Connectivity.Application.VaultBase.dll
Connectivity.Common.dll
Connectivity.Common.Vault.dll
Connectivity.Explorer.Framework.dll
Connectivity.Proxies.utils.dll

Doug Redmond
Software Engineer
Autodesk, Inc.