Apparently, nobody has ever tried to do this so far, since the mac partition handling code in the Linux kernel had no provisions for enabling auto-detection of md software raid.
I've now written patch for Linux 2.6.8, available at http://gnumonks.org/ftp/pub/patches/linux-2.6.8-mac-autoraid.patch implementing this feature. All you need to do is apply that patch, and make sure your md partitions have the type 'Linux_raid_autodetect' in the mac partition table.