TWT,
Is it possible to secure Apple and Android devices to the same (not perfect) standard as Blackberry's ?
Can't speak much for Android, but its certainly viable with Apple.
For a start, the platform itself is very solid and stable. If you don't jailbreak an iPhone/iPad it has a very small vulnerability footprint.
There are already enterprise deployment tools available (for free or little cost I might add... especially compared to the expense of Blackberry and BES Enterprise !). The more large customers Apple gets onboard, the more features the enterprise tools will gain.
But the existing Apple tools already cover most of the core bases e.g. ability to set key restrictions (e.g. no app install, no camera, no you tube, no iCloud etc. ). And it works well .... for example, if you restrict camera usage, the iPhone hides all references to the camera (i.e. no camera app to be seen).
With Apple's APNs service (free at point of use, just need a low cost developer account to get a certificate) corporates can push notifications to intranet apps they may build. No need for Apple servers either, you can push messages from a 5-10 line PHP/Python/Perl script ! Push email is a given with Exchange and probably other major platforms too.
A colleague and I have recently switched from Blackberry 9900s to iPhone 5s and I tell you, I'm not bemoaning the loss of the Blackberry.