You may want to test the SyncForegroundPolicy group policy setting. When enabled, you should see the Software Installation splash banner before the logon dialog.
"This policy setting determines whether Group Policy processing is synchronous (that is, whether computers wait for the network to be fully initialized during computer startup and user logon). By default, on client computers, Group Policy processing is not synchronous; client computers typically do not wait for the network to be fully initialized at startup and logon. Existing users are logged on using cached credentials, which results in shorter logon times. Group Policy is applied in the background after the network becomes available.
"Note that because this is a background refresh, extensions such as Software Installation and Folder Redirection take two logons to apply changes. To be able to operate safely, these extensions require that no users be logged on. Therefore, they must be processed in the foreground before users are actively using the computer. In addition, changes that are made to the user object, such as adding a roaming profile path, home directory, or user object logon script, may take up to two logons to be detected."