You can copy the binary file (who should be in "mylib.framework/Versions/A/") and the headers ( ".h" who should be in "mylib.framwork/Versions/A/Headers")
like this
<source-file src="libs/ios/mylib.framework/Versions/A/mylibBinary" framework="true" />
<header-file src="libs/ios/mylib.framework/Version/A/Headers/mylibHeader.h" />
...
You also have to add the dependencies manually, IE.: this framework needs the iOS AVFoundation.framework so, you need to add this too.
<framework src="AVFoundation.framework" />
One more thing you have to know, if you want to submit this plugin to PhoneGap.
Plugin Submission Guidelines
Any application that contains binary libraries will be rejected. This is because we need to be able to see exactly what is in a plugin as part of our code review process. So when submitting a plugin make sure that it doesn’t contain binary libraries. (PhoneGap)