This morning, leaked documentation and video showed up for Actiongram, an upcoming media creation app for the Microsoft HoloLens. As it turned out, a leaked how-to video for the Actiongram app also shows the Windows 10-style start menu for HoloLens as well.
The menu is shown near the beginning of the video, demonstrating how the HoloLens user brings up what the narrator calls the "shell". In fact, it is a Windows 10-like menu, complete with tiles that show apps like the Microsoft Edge web browser, a video app and more. You can also see the Cortana digital assistant near the top of the shell. A command with the finger brings up the "All apps" menu, which again is similar to the one found in the start screen for Windows 10.
While we will likely see some changes and improvements to the HoloLens "shell" menu before it is publicly released, the video shows that Microsoft is sticking with Windows 10 as its base operating system for all of its devices, from smartphones to tablets to PCs to the Xbox One console.