Is there any way of knowing which ad loaded in an ADBannerView, or in any way control the ad that loads?
There isn't anything on the interface to interogate which ad was loaded when you receive the bannerActionDidFinish callback. I am guessing that the advertisingSection property (currently reserved for future use) might contain some meta data about the loaded ad, but that is just speculation.
There isn't a way of controlling what the ADBannerView loads programmatically. You can explicitly exclude keywords via the admin interface.