You can invoke BBM and use the "invite to BBM" feature to add contacts to BBM. Your application can pre-populate the invite list. There isn't a way to do this without some user interaction. Details on the invocation can be found here: https://developer.blackberry.com/native/documentation/cascades/device_platform/invocation/bbm.html
There isn't a way to programmatically obtain a list of BBM connected apps. But you can obtain a list of the user's BBM contacts who also have your application installed. This sample shows how to do that: https://github.com/blackberry/Cascades-Samples/tree/master/bbmcontacts