Isn't it an amazing interesting coincidence that everybody's personal preference for phone almost always happens to be the same one they get paid to work on?
Seriously, just because you work on something, doesn't mean you have to pretend you're the target market.
There is some value in dogfooding. Perhaps he might be better able to envision and guide the Android teams if he were using one every day. What Android is doing right/wrong may be easier to tell when he has one rather than sifting through customer feedback.
Besides all this are the PR/consumer confidence aspects of this, which I think a company is responsible for managing. To some degree, your success in business depends on what the public perceives of you.
I highly doubt a blackberry is his only phone, I suspect he's got an iPhone, a WP7, maybe even a WebOS phone hanging around.