Can I hot plug the DataVault?

Yes. You can hot plug the DataVault, meaning you can plug the drive or unplug the drive while the computer is on, only with PCMCIA/USB2.0/FIREWIRE connections.
Even though the drive can be hot plugged, an unsafe removal error can occur when the drive is disconnected from a system.

Also look for the safe removal of the drive on the How do I safely remove the DataVault while the computer is on? page.