Curious about this as well. There may be something, but I can't think of any technology that can penetrate stone, other than X-ray, and you need a detector on the other side to see the image...
So not sure it would have worked in that case. The statues where basically used to fill the space (mixed up with other things) when the wall (Jubé) they were on was removed on the 17th century (iirc).
There were some large (known) cavities around, which is the floor based heating system from the 19th century. The discoveries have been made below/around the heating system.
(The other known pieces of the Jubé, now at the Louvre, had afaik been discovered when the heating system was installed in the 19th century, so not a surprise we found more of them when searching the same area)
