A quick test shows that rendering in 360 panorama, then converting to light probe in HDR Shop works.  In the example below, I rendered the original image in 2:1 format, 360 perspective; then into HDR Shop to convert, back into Bryce.  The spheres and ground plane are native, the backgroud and lighting are HDRI.

Come visit us at RenderGods.

Ignore the shooty dog thing.