Regular voxel grids and RTX accelerated ray tracing
As you said, the RTX Turing architecture comes with wired primitive-ray intersection, (to be more specific, triangle-ray intersection). The BVH is built by specifying the Bounding Box program to OptiX, the signature of which is:

RT_PROGRAM void my_boundingbox_build_program( int, float result[6] )


As you can guess, the result must contain the minimun (3 first components) and maximum (3 last components) bounds of the bounding box. You can use this to build virtual bounding boxes even if you have no geometry (for instance, a chunk of 16x16x16 voxels).

When you perform rtTrace , the OptiX API will detect the collision through the BVH which it has build with the help of your bounding box program. In that momment, it will call the Intersection program, which you can specify and which signature is:

RT_PROGRAM void my_intersection_program( int prim_index )


Where you will report any possible intersection within your 16x16x16 chunk of voxels (obviously you can ignore the prim_index, which is only useful when using geometry primitives). 

Now, if you would use their special structure RTgeometrytriangles , the Turing RTX architecture would be able to make use of the wired primitive intersection, which is where performance boost would be gained, and you would not need to implement your own intersection program.

To sumarize:
Since you are not using the specific RTgeometrytriangles , you will not access the intersection performance boost from the Turing architecture.