Infinite-scroll in a single page of a Cutom Post Type

check this page:
http://codex.wordpress.org/Conditional_Tags#A_Single_Page.2C_Single_Post_or_Attachment

Should be something like:

replace

if( is_page('news') )

by

is_singular( 'celebrities' )

Sorry

function my_load_infinite_scroll( $load_infinite_scroll ) {
        if( is_singular( 'celebrities' )) {
            return true;
            return $load_infinite_scroll;
            }
        if( is_page('news') ) {
            return true;
            return $load_infinite_scroll;
           }
    }
    add_filter('infinite_scroll_load_override','my_load_infinite_scroll');

This should work.

If this doesn’t work, you should try and post on the plugin support forum:
http://wordpress.org/support/plugin/infinite-scroll

function my_load_infinite_scroll( $load_infinite_scroll ) {
        if( is_singular( 'celebrities' )) {
            return true;
            }
        if( is_page('news') ) {
            return true;
           }
        return $load_infinite_scroll;
    }
    add_filter('infinite_scroll_load_override','my_load_infinite_scroll');