<?php
function ra_bp_multinetwork_filter( $prefix ) {
	global $wpdb;

	if( $prefix != $wpdb->base_prefix )
		return $prefix;
	if( $wpdb->siteid > 1 )
		return $prefix . $wpdb->siteid . '_';

	return $prefix;
}
add_filter( 'bp_core_get_table_prefix', 'ra_bp_multinetwork_filter' );

function ra_bp_multinetwork_meta_key_filter( $key ) {
	global $wpdb;

	$active = current_filter();
	if( $wpdb->siteid > 1 && substr( $active, 0, 3 ) == 'bp_' && substr( $active, 0, strlen( $key ) ) == $key )
		return substr( $key, 0, 3 ) . $wpdb->siteid . substr( $key, 2 );

	return $key;
}
add_filter( 'bp_latest_update_meta_key', 'ra_bp_multinetwork_meta_key_filter' );
add_filter( 'bp_favorite_activities_meta_key', 'ra_bp_multinetwork_meta_key_filter' );