The code and UI of apachesolr are prepared for different environments (indexes).
But currently most of the setting forms in the UI for the non-default environments are blocked.
I created a patch to unblock these forms and fixed some remaining issues in the code for that functionality in the UI. I guess, these issues might have been the reason for blocking the features.
Having these issues fixed additionally allows to run the cron indexer for all writable environments.
FAILED: [[SimpleTest]]: [MySQL] Repository checkout: failed to checkout from [git://git.drupal.org/project/cck.git]. View
FAILED: [[SimpleTest]]: [MySQL] 110 pass(es), 5 fail(s), and 0 exception(s). View