It absolutely has masking capabilities. However, I absolutely cannot figure out how to work them, so I'm not sure what kind of masking it is. Which is pretty much my experience with Blender in a nutshell...

I don't know how Blender compares to Cinelerra because the last time I tried Cinelerra it managed to crash X. Granted, this was a long time ago, but I ended up in Blender not because it was superior as an editor but because it was superior as a program that didn't crash X. Now I have so many projects invested in Blender that even if this Lightworks project works out (sounds cool! I hadn't heard of it) it would be difficult to bring myself to switch.