After much mayhem and testing i figured it out.... It was all dandy and fine if i just used the proper type of the variable... It had to be String&.. The way i got this was by the line:
methodInfo.GetParameters()[0].ParameterType.UnderlyingSystemType
Further as i tried this the code looked like this:
Assembly assembly = ResourceConfig.GetAssembly("IntegrationServices");
BindingFlags bindingFlags = BindingFlags.Public | BindingFlags.Static | BindingFlags.InvokeMethod;
MethodInfo methodInfo = assembly.GetType("Current.IntegrationServices.SomeIntegration").GetMethod("GetAbaxUserToken", bindingFlags);
var staticMethodWithArgs = assembly.GetStaticMethodWithArgs("Current.IntegrationServices.SomeIntegration.ReturningMethod", methodInfo.GetParameters()[0].ParameterType.UnderlyingSystemType);
Which in turn led me to invoke the MethodInfo, and drop the GetStaticMethodWithArgs concept... If anyone knows how to get the type String& in this manner, without crashing: typeof(String&) I would be greatful :)