<p>Is there any way to add iCal event to the iPhone Calendar from the custom App?</p>

Yes there still is no API for this (2.1). But it seemed like at WWDC a lot of people were already interested in the functionality (including myself) and the recommendation was to go to the below site and create a feature request for this. If there is enough of an interest, they might end up moving the ICal.framework to the public SDK.
https://developer.apple.com/bugreporter/