"So does that mean that I can export the scenes (including trees, terrian, rocks and all their textures in one fell swoop to Poser 5, allowing me to incorporate my Poser Characters from that end, and thus still make use of the cloth room after all?"

I would like to know this as well but for Poser 4.

For me, it can be very tricky trying to pose a figure in poser then import it into Vue and see how the footing does not line up with the ground. This leads me to have my ground usual flat when I have figures on them or I hide the foot going through the hill with some bushes. This would stop this problem as I would be working backwards(make the scene in Vue, export it into Poser 4 for people placement)