The question has come up several times about whether it is possible to run the ITMU version of patchinstall from a command line. In short, the answer is no.
When you execute the ITMU version of patchinstall from command line, using the same parameters as you use to successfully execute the package from within SMS, you will notice that patchinstall correctly starts the initial patch scan and waits for it to finish - but when it finishes patchinstall simply exits.
The reason for this is that in ITMU patchinstall is not used for patch installation. When ITMU patchinstall is launched through the SMS client CCMExec intercepts the call and redirects it to run a different method. When executing from command line - or even OSD - CCMExec can't intercept the call to patchinstall for appropriate redirection.
This is a known issue and a bug has been filed with development that is currently going through the evaluation process. As a workaround, there are at least a couple of 3rd party scripts available to allow patch evaluation during OSD at www.myitforum.com - just search for ITMU and the resulting list will contain the article discussing this.