In /init the check is done if the RAID array UUID's are same as the ones stored in EEprom. If not, the box doesn't boot. Fortunately,
there is a check to see if it are 'new disks', which can be found in /lib/lacie/libcommon:
# We store firstboot signature (LaCieFirstBootLaCie)
# in the beginning of the 3rd sector.
# (19 bytes + newline = 20 bytes)
so you should execute
echo "LaCieFirstBootLaCie" | dd bs=1 skip=1536 of=/dev/sdb
on each disk, to make it 'new'. (Of course you should exchange /dev/sdb by the right value.
(fortunately this space is not used on most disks, so an error shouldn't hurt.))