Licensing on the 3300 works a bit different... You can setup an Enterprise Network using Enterprise Elements (a more expensive base license) with a DLM (Designated License Manager, another license), and "share" licenses... Basically meaning you assign them to the devices primary node, and then you can have a Primary and Secondary host for each device. If connection to node A is lost, the phone automatically homes to node B, and when the connection is restored the phones home back to node A. It is resiliency, NOT redundancy, but works well...
The phones are resilient, but not redundant. It does take a fair amount of back end work with trunking and other stuff to make it work, but it works well when implemented correctly. The cost for a resilient 3300 setup is significantly more than a MiVO 250... Let's say your MiVO 250 setup was $50k with MiVO Application Suite for 2 nodes for 100 users (just simple numbers to make it easy, not real)... I could really get into it with VMware/Vmotion and servers that are not co-located and other stuff, but it's not relevant, the reality is going to cost 20% to 100% more than a MiVO 250 setup depending on the setup and level of resiliency you want, and because you are shifting from a hybrid Key/PBX to a true PBX your feature sets change and some things become more difficult to do on a MiVB.
I have implemented these system in a scale of anywhere from 20 devices at a single golf course, to companies spanning the globe with offices and PBXs networked in dozens of cities and doing resiliency for other sites across the globe for not just phones but MiCollab and trunking services being resilient as well. The biggest thing I see with resiliency is it is poorly implemented... Yeah, if the phone go down in Minneapolis they will rehome to Los Angelos, but what about those trunk calls coming in a PRI? What about the voicemail/AA now that those 200 phones are failed over? What about the bandwidth considerations of a 200 phone call center now make and receiving calls from a site on the other side of the country with 8 SIP trunks and 50 users? The answer is it can all be done if it's setup properly, but it costs money and most of that investment is unused 99% of the time... Anyway, you see where this going.
Sorry... started rambling again...