After a quick search I only managed to find one, maybe two fake BBM apps. Compared to a few dozen on Android around the time when BBM got released. While this doesn't justify the existence of those WP fakes, it still could be much worse.
My theories regarding BBM release are:
1. They learned from their rough Android and iOS launches and want to make sure their WP launch is going smoother.
2. I am very sure BlackBerry is in touch with Microsoft regarding their WP 8.1 roll-out. It could be quite possible BB is waiting for the first roll-out to happen, since multiple sources are already stating it would happen during the first two weeks of July.