I don't know what they would do with the passe PDAs, but the move actually makes sense. BlackBerry's parent owns a trove of patents for increasing connectivity in cars. GM could move quickly forward in this increasingly important area. It would be a much better move than the company's investment in either Ally or exploding cars.
You can write this off as one of my crazy ideas, like about 10 years ago when I said Ford should hire its next CEO from Boeing.