KaTracker supports external torrents, but only in the tracking actions – it means that you cannot show stats of an “external” torrent, or get to it’s information. You can enable the open tracker option in the settings page.
Seed/leech stat can be a little tricky if you use an external caching system (although for what I’ve seen it’s working fine with caching plugins).
If you mean that the stats does not show when using the shortcodes, note that the shortcodes are very minimalistic right now, and lacks many options (you can list all the torrents with [torrents (category=…)] – also show basic stats, or paste a link to specific torrent with [torrent id=…] shortcode). If you want to implement your own shortcode structure in your theme, you can copy and edit the existing “katracker-shortcode.php/.css” to your theme directory and edit them as you wish.