When opening in Nik software it states that you can transfer with LR attributes. This allows all work done in light room to stay when opened in Nik program. Hence when transfering a file to Silver Efex Pro it keeps all the setting from lightroom while changing it to B&W Neutral setting, and you can go from there.
The integration is noce, though a little slow. I really like the rendering of silver Efex Pro, though.
So long story short, the colorspace stays the same.
|Douaumont Ossuary by Eric 54-BNF|
from Armistice Day
|Silhouette at sunset by Jill Hancock|
from Portrait Lens (around 80mm or equivalent - please check the full rules)