BlackBerry Messenger coming to Iphone? What are they thinking?

According to some articles and a recent interview with someone from blackberry and apple, it seems that blackberry messenger is coming to Iphone and will work with ios 6 and over. I have both a blackberry and an Iphone and I don't see why they would bring it. Dn't get me wrong it would be great, but as a business decision, why?

Why would they bring bbm to Iphone when their are other messaging services in the app store?
Why would they make it a free app but continue to charge their blackberry users £5 a month?
Why would they add skype to blackberry's when the defeats the whole purpose of using bbm?
Why would they add blackberry facechat on the new blackberry z10 when skype will have facechat aswell?

Do you think this is a good business decision? It seems to me that it doesn't make any financial sense.

Why would they bring bbm to Iphone when their are other messaging services in the app store?
To stop people from buying those other apps

Why would they make it a free app but continue to charge their blackberry users £5 a month?
Not to say they wouldn't do the same here. The app itself maybe free, but the service for it is not

Why would they add skype to blackberry's when the defeats the whole purpose of using bbm?
Skype is a popular VoIP app. The more apps the better, & they certainly need it at this point

Why would they add blackberry facechat on the new blackberry z10 when skype will have facechat aswell?
Nothing wrong with offering features.