Scalable for what exactly? Nokia is a the largest mobile phone manufacturer in he world, Nokia makes mobile phones, lots and lots of mobile phones. Clearly any scaling of that OS is to be done with a somewhat focus on phones. Surely you can shoehorn an old steam engine into a car and achieve great power, but a modern turbo engine would be a much better fit. In fact it is an excellent comparison. WP is a modern engine, fast, compact, reliable. Linux is the old smelly, noisy and inefficient steam engine.