So you know that Cubasis has IAA now, here's the rest too

Of course you might of missed it as it's pretty recent, but here's the full details on the update:

FULL INTER-APP AUDIO SUPPORT

• Use Inter-App Audio apps as insert/send effects.
• In the instrument rack you can choose Inter-App Audio apps as instruments for your MIDI tracks.
• On audio tracks, select any Inter-App Audio app from the routing tab in the inspector to record them.

OTHER

• Audio inputs popup added to the inspector to easily assign tracks to mono, stereo, Audiobus or Inter-App Audio.
• New in-app help system including interactive search function.
• AudioCopy 2.0 SDK has been implemented.