All modules that are located in the official OpenERP modules repository are covered by OpenERP Enterprise, including all country-specific localization modules beginning with l10n_.

However OpenERP S.A. did not write all those modules, and may not be actively maintaining them. They're usually written by local OpenERP Partners in each country, and those Partners are the ones maintaining them (adapting them for changes in the local fiscal rules, etc.)

As those modules mostly contain pre-configured data and no business logic, the chances of finding a coding error in them is rather low, and any problem can usually be fixed by correcting the settings directly in your database. Nevertheless, if an error is found in the data, OpenERP S.A. will do whatever is required to get the module fixed as soon as possible under OpenERP Enterprise.

It is not under the OPW guarantee. (at least for my country) Localizations usually include Chart of Accounts and some legal reports and translations.

You should sit with your accountant and your OpenERP consultant and they should check the every account and every report one by one and change the required reports.

You can change the terms in your OpenERP installation and reports from menu

Settings > Translations > Application Terms