Not sure that I understand it, but here's an excerpt

http://www.tmx.com/en/pdf/notices/2009-024.pdf

Introduction of the Bypass Order

Effective June 1, 2009 a single-sided bypass order will be available for Toronto Stock Exchange ("TSX") and TSX Venture Exchange ("TSXV") listed symbols that will enable trading customers to choose to execute against passive disclosed volume orders while bypassing all undisclosed volume of passive iceberg orders, Registered Trader participation and any Registered Trader MGF boardlot obligations. The introduction of the bypass order assists Participating Organizations and Members in meeting their best price obligations under the Universal Market Integrity Rules (UMIR) by executing against only the disclosed volume on TSX/TSXV before or at the time the Participant executes at an inferior price.