TSX has a trading session called MOC Imbalance, while in this session I see the imbalance fields being populated (IMB_SH, IMB_SIDE, and IMB_PR_REF). When the MOC Imbalance session ends I would like to clear out the imbalance values in my trading system. How can I tell that the MOC Imbalance phase has started/ended?

On the native TSX feed I use the Market State Update message to tell me what trading session TSX is in.