Why does not hook_block_view_MODULE_DELTA_alter work?
That hook is called right before a specific block is rendered. If the block isn't present in the page, the hook is not invoked. Replace that hook with hook_block_view_alter(), and it will get invoked for every block shown in the page.

Bear in mind that Drupal caches the hooks implemented from a module; if you alter the code of an enabled module, Drupal will not know the module has a new hook. Disable the module before editing its code, and re-enable it after editing its code; in that way, Drupal will clear its cache, and notice there is a new hook, using it when necessary.