Spike,
There's a difference between the mod_login Joomla Login module and the standard Joomla Login component view. JFBConnect can modify the component view of com_users (the Users component), but we don't modify the login module, which can be used anywhere.. so altering it could have some bad results. In general, the SCLogin module should replace the Joomla Login (mod_login) module... and JFBConnect can automatically add the social login buttons to the Joomla User Login component view.
Confusing.. probably, but we have most of the bases covered that way.
With that said, the solution to the above is to alter the line the EasyBlog folks gave you and update it to:
$mainframe->redirect( JRoute::_('index.php?option=com_users&view=login' , false ) );
That should redirect to the Joomla component login view, which JFBConnect should be adding the social login buttons too.
I hope that helps, but if not, as always, just let us know!
Thanks,
Alex