Short answer: take out the battery. That's the only way to completely disable the GPS in the phone. Your more reasonable options are "911 only" and "Location On." "911 Only" is the minimum data required by 911 services. "Location On" enables other Location Based Services on non-Verizon phones. Verizon disables the internal GPS on their phones. It can only be used with their subscription based VZNav software. So "Location On" does nothing for you, except transmit information about your position that you can't use.
If your work is using specialized software to make sure it's employees are where they are supposed to be there is probably nothing you can do to block it unless it doesn't use the always on aspect of GPS.
Posted from my CrackBerry at wapforums.crackberry.com