Note that once this change is live, your MCC scripts may start getting more accounts when calling the MccApp.accounts() method. You should check your MCC scripts to ensure they can handle the possible extra accounts. You can restrict the accounts that AdWords scripts return by applying an appropriate filter condition in your account selector.
Note that this change doesn’t affect the way other selectors work. For example, you cannot retrieve an AdWords Express campaign by calling AdWordsApp.campaigns() on an AdWords Express account.
If you have questions or feedback about this change, let us know on our developer forum or our Google+ page.