Hi ArenMook,
with your code, that I have added on my Assets/NGUI/Scripts/Internal/EventDelegate.cs script, when I run my WP8 solution throw the MissingMethodException.
This code is compiled by Unity inside the Assembly-CSharp.dll.
When I choose Windows Phone 8 Platform inside Build Settings options, and I click on Build... button, Unity compile Assembly-CSharp.dll (it compile also NGUI source) and create a Visual Studio Windows Phone 8 Solution.
When I run on Emulator or Device (it's the same), and press my button created by UIButton NGUI Script, with a Notify, it crash.
It is like Unity (4.3.4f1), when compile for WP8 Platform, build as the define symbols REFLECTION_SUPPORT is defined.
I'm using NGUI 3.6.5 with Unity 4.3.4f1 on Windows 8.1 Pro.