폼 생성(Create) 이벤트에 아래와 같이 추가했습니다.

//PC/SC Devie WndProc Event Set
DEV_BROADCAST_DEVICEINTERFACE filter;
filter.dbcc_size = sizeof(filter);
filter.dbcc_devicetype = 0x00000005; // on the interface
filter.dbcc_classguid = SmartCardReaderGuid;
m_hInterfaceNotification = RegisterDeviceNotification(Handle, &filter, 0);


//---------------------------------------------------------------------------
//WndProc
//---------------------------------------------------------------------------
void __fastcall Tfpluginmain::WndProc(Messages::TMessage &Message)
{
    //Device Insert/Eject Event
    if (Message.Msg == WM_DEVICECHANGE)
    {
        //Device Insert
        if (Message.WParam == DBT_DEVICEREMOVECOMPLETE)
        {
                //Form show
                Show();
        }
        //Device Remove
        else if (Message.WParam == DBT_DEVICEARRIVAL)         
       {           
                //form Hide
                Hide();
        }
    }
    //Windows Message
    else TForm::WndProc(Message);
}

로 수정했구요.

정상적으로 이벤트가 뜨네요.
수고하세요.