Is this ice cover real - and what circumstances are required to make it?
Yes, it is real. Whoever took the photo, congratulations on a very fine image.
I have never seen this texture on such a scale, but something similar can be achieved in the laboratory by creating a bubble membrane of pure super-cooled water and blowing a few dust nuclei onto the surface. A comparable geometry appears very rapidly. The size of the ice crystals are difficult to judge without any feature to give scale, but they seem to be exceptionally large trigonal terminations. We have all seen snowflakes of hexagonal symmetry, but under metastasble conditions with rapid crystal growth, stacking disorders tend to occur in the crystal lattice, yielding a trigonal rather than hexagonal symmetry. See, for example, The ice phases of water. This is an unusual polymorph of ice, and I cannot see how it could be achieved except through sudden seeding of very pure water. Perhaps stratified freshwater lakes, in still air, on a very cold night, with a surface of previously melted ice (i.e. pure water), and subject to a sudden windy gust of nucleation particles would provide the right conditions?