Another Pov-Ray user here and (as usual) late to the discussion (would be much easier if we had a Pov-Ray forum here, but that's a gripe for another thread, lol).

Poseray can import entire scenes, you just have to export everything as an obj (click the universe box in the export window) then open the pz3 file in Poseray and tell it where the obj file is (if that makes sense).  Poser's procedural textures won't import, but Pov-Ray has it's own procedurals that are really nice once you get the hang of it.  I've used Pov-Ray procedurals to create textures for a book model where I just give it the basic colors and title and the computer makes the texture - nothing too detailed, but useful for filling a shelf with hundreds of books in a few seconds - I can post the model and texture code somewhere if anybody is interested (I'm almost always willing to share anything I make, but there's usually not much interest or nowhere to post it here where it wouldn't be off topic cough Pov-Ray forum cough).  The books on the shelf in the background in this image were made with it. 

http://www.renderosity.com/mod/gallery/index.php?image_id=1326871

I'm not sure about Poser's IBL (I'm still using Poser 5), but Pov-Ray does have radiosity & HDRI though it can be tricky to set up sometimes.

I usually just export individual objects from Poser and set up my scenes in Pov-Ray itself since I also do alot of my modelling in Pov-Ray.  If I'm going to be changing the textures (Pov-Ray can do excellent metallic and glass materials), I even export the people and clothes as separate obj's to make the mat files easier to deal with.  I've used Pov-Ray for a while now, so for me at least, it's easier to tweak things like textures and lighting from Pov's text files.  Or at least I seem to get better results that way, lol.

Everything in my gallery here was at least rendered in Povray and most were set up and at least partially modelled with it.