Quingees Tatts and Tabcorp have pricing power as they do create their own betting odds....
The ACCC cares about a substantial lessoning of competition which may result in prices going up for consumers.
As 'Ildsrud' said, they don't market their own products, don’t charge the consumer for their service so hence the consumer would not be paying more if they combined.
The only issue may come from the insurance companies that pay ISU to market their products however as comparison sites do not make up more then approx. ¼ * of insurance sales, I don’t see this being an issue.