I found out that the short curved section in the middle of the Trans-Siberian Highway is just an urban legend, probably based on a similar tale about the Moscow-Saint Petersburg Railway. Here’s the real story:
Nicholas I is involved in a common misconception about the railroad from Moscow to St. Petersburg. When it was to be constructed, the engineers proposed to Nicholas to draw the future road on the map himself. So he is said to have taken the ruler and put one end at Moscow, the other at St. Petersburg, and then drawn a straight line. But as his finger was slightly sticking out, this left the road with a small curving. In fact, this curve was added in 1877, 26 years after the railway’s construction to circumvent a steep gradient that lasted for 15km, and interfered with the railway’s functionality.
The “Tsar’s Finger” has since been sliced off (http://www.guardian.co.uk/russia/article/0,2763,579665,00.html). A similar story is told about Josef Stalin who, when presented with two different plans for the Moskva hotel, signed across the middle of the two. As the architects were too frightened to ask Stalin which plan he wanted, both designs were used and the hotel, still standing just off Red Square, has two different facades.