Blackberry officially announced on their blog today that they will gradually start rolling out BBM for both Android and iOS today. They said in a couple of hours, the app will appear in Google Play and the App Store. It will likely be a gradual roll out so they don’t overload their system at once though.
They however stated that the easiest way is to visit BBM.com with your Android or iPhone browser to get the app. Once you install the app, open it and enter your email address to hold your spot in a waiting list.
They will then email you as soon as you reach the front of the list and can start using BBM.
Blackberry is probably being so cautious based on the problems they had from the previous failed launch of BBM. Even though they did not officially release the app for Android at that time, it has been estimated that in just seven hours, about one million Android users were using the unreleased version of BBM for Android. Also that one million people have found creative ways to “side load” BBM on their iPhone. This is why they are doing the whole list thing.
To get full details, check the Blackberry blog