Use a web proxy (like Charles Proxy http://www.charlesproxy.com/) to watch the network communication between the simulator and the various hosts. You may have to get it configured to use SSL which is tricky.
You can also get it to work with an actual device you can also use your dev machine as a proxy, that's a real bear to get working depending upon your networking situation.
Note: I've not actually done this for iAds, but for other traffic I do it all the time. I've no relation to Charles Proxy except as a very satisfied customer.