[Plugin: Jetpack by WordPress.com] Can't replace media shortcodes

We’re running Jetpack on a network of 50 or so sites and love it. One of the things that we’d like to do, though, is supersede the blip.tv shortcode to play using our custom player rather than blip’s built-in player. I created a quick plugin in a z-plugins directory so it would load last that looks something like this:

remove_shortcode( 'blip.tv' );
add_shortcode( 'blip.tv', 'bdn_blip_shortcode' );
function bdn_blip_shortcode( $atts ) {
	//return my shortcode junk
}

I tried both with and without the remove_shortcode (WordPress doc says it isn’t needed) and didn’t have any luck. Has anyone else tried this? Are Jetpack modules possibly being loaded in a way that would prevent this?

http://ww.wp.xz.cn/extend/plugins/jetpack/