WP-CLI works on non WP-CLI installed WordPress instance?

I came across WP-CLI via the tutorial at http://centminmod.com/nginx_configure_wordpress_ffpc_plugin.html and was wondering does WP-CLI work on WordPress instances which were NOT initially installed with WP-CLI but installed via normal FTP upload WordPress installs ?

So can I manage plugins, core updates via WP-CLI on non WP-CLI installed WordPress installs ?

Yes, of course it does, as long as you also have SSH access to the instance (it won’t work over FTP).

There’s nothing special about WordPress instances installed via WP-CLI. Commands such as wp core download and wp core install perform the same actions you would normally do when installing manually.