Can I enter my license key via command line?

I’m trying to install Unity on a remote Mac server via command line, and I have a Unity Pro license key that I’d like to activate.

Unity - Manual: Command line arguments indicates that it’s possible.

Activation needs to happen using the GUI. There is no command-line based activation possible.

With Unity 5.5.3f1 I was able to get this to work:

"c:\program files\Unity5.5.3f1\Editor\Unity.exe" -quit -batchmode -nographics -serial <key> -username "<username>" -password "<password>"

Also, returning the license via command line worked:

"c:\program files\Unity5.5.3f1\Editor\Unity.exe" -quit -batchmode -nographics -username "<username>" -password "<password>" -returnlicense

I was unable to get either to work under 5.1.1f1.
The company I work for has to manage over 50 licenses across about as many automated build machines so this is a critical feature - especially when the build machines randomly “lose” licensing and need to be reactivated for no apparent reason.