This is not based on any evidence other than the resignation letters and my knowledge of the practices of another China RTO learned from a conversation with the CEO of that company.
It is possible that, to win contracts with bus companies, CCME had to do favors for the companies or their executives. Those favors may be included allowing bank accounts to be pledged as collateral for loans made to the executives or the companies. These would result in bank balances still agreeing with CCME's financial statements, but would be restricted cash, unavailable for withdrawal while the 3d party loan was outstanding.