It's not magic, it's been done before. It just usually leads to poor sales in a consumer focused devices, as rooting was something that Android power users expected.
Now if the PRIV is a enterprise focused device... they I expect it will have a locked boot rom. But I'm afraid that most of the things that will make the PRIV attractive to the enterprise customer, will make it unattractive to the average consumer who would rather not have their battery life affected by 10 different BlackBerry Experience Apps running in the background.
I hope there is an "App" to easily turn off or on all the BlackBerry stuff....
I think if they want both markets, they should consider what HTC used to do. Official unlock, but consider your warranty void if you so choose so, we can't guarntee the security of the device once that is done.