Catalan and Basque resources in Android
Actually not all languages are documented at Android docs and many brands did your custom version of Android which may change its list, but be sure that if a device has Catalan and/or Basque suports it will use ISO standard, and the values will got rigth as it is converted with string comparision.
Maybe it would be a good choice to put a handed changer if you got that most devices do not have this support on your tests.
Many devices ship with a limited selection of languages in the settings menu, but can actually be set to any system locale using an app such as LocaleSwitch.
It should be pretty easy to test whether Basque is supported by adding a custom locale in LocaleSwitch and then adding the resource folder to see if the system loads the resources from this folder automatically.
Finally, Gingerbread 'support' for Catalan may only reference the inclusion of android.R values since 2.3, though I can't see them in the framework repository.