(Drupal 7) List blocks being rendered by the Context module into a given region

context.php

<?php

// Grab an instance of the "Block Reaction" plugin.
$context_reaction = context_get_plugin('reaction', 'block');

// Run the block_list() function to find the blocks being rendered
// into the region you specify.
$context_blocks = $context_reaction->block_list('REGIONNAME');

// Now make sure that we reset the static cache for the block list in case
// Context isn't done adding blocks to the region for any reason.
drupal_static('context_reaction_block_list', NULL, TRUE);