Access plugin post type from another plugin

Hi everyone,

Here is my problem. I have installed The Event Calendar Plugin, wich creates some custom types (let’s say Events).
What i want to do i use these custom post types in my own plugin. I want to extend my XMLRPC functions to use them.
The problem is that i can’t access them in my plugin. It’s like they not already exist. Some functions like get_post_types() returns only the basic custom post type (even with the arg:

$args=array(
  'public'   => true,
  '_builtin' => false
);

).
Same thing for custom taxonomies. Any idea on how to solve this please?

Thanks!