miniBB has not changed its integration flexibility in the new version at all, but just extended it. What you see in the new layout is just a default CSS which still can be integrated in almost any layout. You may check these threads for more understanding what happens:
How to choose the thin ( slim ) layout (this is about how you can switch to the older layout schema of miniBB)
New version's press release and discussionIf you will have more [exact] questions don't hesitate to ask!