It depends from how custom post type (CPT) is defined. WordPress core register_post_type() has ‘show_ui’ parameter. If CTP is defined with show_ui==FALSE then you will not see it, even is you administrator.
If CPT is viewable by user with enough permissions, then it’s possible to manage who can view them. Look at this article.
Take into account that, some plugins use internal data structure for their records instead of WP custom post types.
