Toni-IP Phone has a tandem feature that allows it to take control of a desktop phone, this is neither Telecomuter nor RoadWarrior mode. It's so you can use IP softphone at the same desk as your physical phone. I use it daily, it is quite handy.
I'm not clear on exactly what your concern is. For a user to use IP Softphone, they must have an extension with a valid security code. They can't just access any extension on the switch unless it has security code and the user knows it, and it's configured for IP Softphone use. Do you simply not want them using the Control Phone mode at all?