ComEd confirms that your understanding is correct. Item (ii) of the assignment provision, as provided in your question, allows a winning bidder to assign the Master Agreement to an affiliate whose creditworthiness is equal to or higher than the creditworthiness of the winning bidder. In the case that you provide, both the winning bidder and the assignee have the same creditworthiness as neither company would be granted unsecured credit under the terms of the Master Agreement.
Please note that any bidder not granted unsecured credit under the terms of the Master Agreement must provide either a Letter of Credit or Cash Collateral as performance assurance.