OK, so I received your email.
I’m not sure exactly what code you’ve put in place beyond what Rob suggested in that tutorial, but you would probably also want to modify the tag taxonomy so that it works with event posts.
By default it works only with regular WP posts – so although you may now be able to tag events that doesn’t mean you’ll also be able to query for them directly as you would for posts with a specific tag.
Take a look at:
http://codex.wordpress.org/Function_Reference/register_taxonomy
And the registered_taxonomy action hook – they might offer a path forward here (there are also lots of comments and alternative strategies in the comments for that tutorial).