something like this maybe? (or have I misunderstood?)
private void CallCustomerSubInformationDialog<T>(int iMode, T iCustomerInformationObject) where T: GenericCustomerInformation, new()
{
//where T is either Emails or PhoneNumber
GenericCustomerInformation genericInfoItem;
//This is what you could try to do:
genericInfoItem = new T();
}
NB: Note the constraints on T...