From the article,

"a) never cold call each other’s employees; b) notify each other if making an offer to an employee of the other company, even if that employee applied for the job on his or her own without being recruited; c) any offer made would be “final” so as to avoid a costly bidding war that would drive up not just the employee’s salary, but also drive up the pay scale of every other employee in the firm."

I think it's clear how this would affect wages.