> Quite likely to release a W- boson.
Possibly, if it interacts at all. This is still a vanishingly small probability, even if high compared to other neutrino energies.
10^15eV is an astonishingly high energy. About 1,000 times as energetic as a proton in the LHC (which benefits from a gigantic rest-mass). To generate enough of them to be detected is seriously the realms of ultra-science fiction. Along the lines of turning Jupiter into a star or building a Dyson Sphere.