Thanks for the kind comment Chris. You should follow my ramblings at blog.michaeltoye.com. I post London images and, every so often, "how i processed/took/did..." pieces.
The taxi/bike shot was not a special process. In point of fact, all my images are processed in the same fashion. I use CS6 and Silver Efex Pro 2, which I can see why it was given freely by Leica. Cracking product!
I produce a 'base' layer which might very well look like the portrait of your girls above - good level of contrast and most importantly a lovely range of tones. maintain control of the light levels in the base layer too, as you have done.
Not sure where the equivalents are in other products, but I use 1 or 2 contrast layers in addition; Soft & Hard Light Blend Mode. They will amplify blacks and whites.
To achieve this, I will process an additional layer in SEP2. Low contrast, even tones, maybe a vignette. This layer will be set to soft/hard light layer mode. There is practice in knowing how the soft/hard light layer modes will react with this additional image layer though.
It's this extra step that reveals the deep blacks.
Hope this helps
Michael