Do you mind if I mock your attempt to suggest that a phone which is is probably several million lines of code developed by a company which has a relatively small user base on the new code base and just hasn't been a real hacking target yet is secure?
The old Blackberry might have been secure if for no other reason than it was a glorified PDA without the ability to do much of anything dynamic. The new version is based on QNX makes heavy use of message passing APIs (which I personally have evaluated the code for and will agree that part is secure. At least in transit) but will be coded for by developers who will focus on usability and functionality which will require their apps to become subscribers to many message pipes and eventually will become sources for information which they didn't originate and therefore will become backdoors in the phone allowing pretty much any other program to hack the data when the user really only permitted access to that data to the one app.
QNX IS NOT a UNIX, it is mostly POSIX. It is an embedded real-time operating system. It has a pretty interesting scheduler and I'd love to poke around to see how they managed to get a real time OS to pretend to be a suitable end user OS (a hell of a task if it worked).
Please also understand that sand boxing is only interesting so long as we don't want information to cross between apps. In truth we do. And we want apps to communicate. Therefore it doesn't matter if the OS is the most secure OS on the planet, as soon as you add third party apps and users that use them, security is shot to hell.
As for basic security of the OS, like "Can someone hack it from the internet" or "Can someone hack into from physical access?". The answers are simple. Yes and yes. We may not know how, but if anyone gave a shit about Blackberry, it wouldn't be that hard. I would of course just abuse social engineering instead as it's far simpler, but I have actually hacked a Samsung using a black light on the screen just moments after the user hung up a phone call. It left a lovely smudge in the shape of the password from the fingers tracing it.
Quit talking security as if it's even possible. Especially with the "my system is so secure and yours isn't", paranoia is good and believing that your phone can and will be hacked keeps your nudie pictures off the web.