The best you can do it buy a spare chassis, then get a virtualized PS-1 in a properly configured multi-server Vsphere environment with Vmotion... The chances multiple servers will fail is near zero, and when running with a PS-1 there isn't a lot going on inside the chassis itself. It is the closest you will get with the MiVO 250.
If you need true redundency/resiliency, you need to look at a MiVoice Business cluster.
