The <shapePath> token gets replaced with the full name of the node as exported to Arnold, with "|" replaced with "_". But only if full paths are exported in the render settings.

e.g. A node named |pCube1|pCubeShape1 in Maya will become _pCube1_pCubeShape1in <shapePath>.

This feature may be deprecated in the future as you can get the node name using <attr:name> instead.