I disagree. I don't see anything extra in the API that can do this, I doubt the OS would break its own rules.
I have just tested "Safely Remove Hardware" and it operates just like the other icons, if it can show the icon it will but if the area is full the icon will be hidden. The same as what happens when I add my application to the tray. This also applies to the Action Center (right now on my machine it is hidden).
What you are trying to do is override how the user has configured the options. Sure, you may be able to hack you icon to show, but if a user has explicitly told the tray to hide all icons apart notifications you honour that and shouldn't be thinking of ways to combat that choice.
The proper way to get the users attention is to show a notification, this what is documented and that is what you should be using.
http://msdn.microsoft.com/en-us/library ... 85%29.aspx
Also see :
http://msdn.microsoft.com/en-us/library ... 11448.aspx
Specifically "Keeping users in control", "Guide lines" and "When to show"