Does a listing agreement supersede a commission clause in a purchase and sale agreement?

The plaintiff cites in support of its position a more recent case in this court of Windsor Italian Village Limited v. Remo Valente Real Estate Limited, [1992] O.J. No. 2213. Brockenshire, J., refers at length to the Liebig case above, and conducts a thorough review of English and Canadian authorities on the question of primacy of listing agreements over commission clauses in purchase and sale agreements respecting commission obligations of a vendor to a selling or listing agent. He summarizes his findings on the question at page 5 in the following terms: Further, I find that the decision…in Liebig now makes it clear that the binding agreement between the vendor and the agent in a modern real estate deal is the listing agreement. The commission "agreement" at the end of an agreement of purchase and sale is not a contract between the vendor and the agent. If the agent wishes to argue that such a commission "agreement" amends or modifies the listing agreement, the onus is upon the agent to prove that this was agreed upon by the parties.