You want blue hour? OK, you got blue hour! Darkened the image in Levels (only the Gamma slider, so as not to block up the shadows), and enriched the sky with Selective Colour (just the cyan and blue).
Hope you don't mind.
You may not agree about the monochrome conversion (many won't I suspect), but to my eye it emphasizes the graphic elements, already strong. The cloning was fairly straightforward, although I realised that I would have to remove the shadows of the cyclists on the left too! What do you think?