Joomla 3.4.7 breaks cron processing

Joomla's version 3.4.7 breaks the CiviCRM cron scripts (both cli.php and cron.php). The release was a security patch addressing problems in some PHP versions, and reworks how session handling is managed. Details here: https://www.joomla.org/announcements/release-news/5643-joomla-3-4-7.html

The problem is triggered by CRM/Utils/Hook/Joomla.php, line 82, where we import civicrm plugins (for hook processing). As part of that native Joomla method call, a Joomla session is instantiated, but apparently is not created properly (or fully), and so triggers a fatal error.

I'm investigating. Any other Joomla devs are welcome to assist.