While it’s possible to register any taxonomy with any post type (as shown in the above – just replace post_tag with the taxonomy, and event by the post type), this is only half the battle…
When viewing a given taxonomy you now have a mix of post types. This can be problematic because:
1. Events displayed differently to other post types.
With events, you’ll probably want to display state/end time as opposed to publication date (as with normal posts). There’ll be other details (venue, etc) which won’t make sense for other post types.
If you are querying only events, then the event templates are used, but if you have mixed post types, they’re not, and your theme’s other templates are used. Even then, displaying events differently is fairly straightforward, in your theme just edit the appropriate template to include an ‘if’ conditional to deal with events and non-events.
2. Events are ordered differently
This is the killer. Events are typically ordered by their start date and posts, by their publication date. It’s very difficult to get events and posts listed together but ordered by different criteria. (You’ll need to adjust the SQL query and make use temporary tables).
:/
