Nexus 10 / Android 5: recovery broken, fastboot not working
Some Nexus 10 tablets have a bug ,the fastboot menu is hiden ,the
screen remain blank even when you are actually in fastboot mod to
make sure you don't miss it do the following
Hold Power + Volume Up + Volume Down until the tablet vibrates twice
(once to shutdown, then a few seconds later to acknowledge fastboot
menu). After the second vibration, you should be in the fastboot
menu, although the screen is blank plug the phone to pc it should be
recognized
Now that you have access to fastboot ,you can flash a new firmware or
a custom recovery to get your device to a working stat.