The card company has the right to be indemnified by the supplier (s75(2)), and has the right to have the supplier made a party to the case (s75(6)).
My view is that the card company's position can end up being neutral: if breach of contract by the supplier is established, it gets an indemnity i.e. the right to be repaid by the supplier. If the court finds no breach of contract by the supplier, the card company has no liability.

Others may have different views.