According to this comment by Tom O'Connor (slightly edited below):
You can seriously cheese off a datacentre by putting an UPS inside your own rack.
What are the risks to the data center should a customer (somehow) choose to do this?
We have an air-gapped Windows Server, not connected to the public or private network.
There are a number of routine tasks that must be performed on this machine after hours. These have been automated using AutoIt scripts.
Now, as you may know, AutoIt commands such as ControlSend and ControlClick can operate in a kind of headless mode, with no window manager being available. However, WinActivate, Send and MouseClick all require the workstation to be unlocked. Unfortunately, due to the nature of some of these tasks (and current limitations of the software they interact with), we must use the later commands. Therefore, the workstation must be unlocked.
Is there any way to unlock Windows programmatically? Everything I have read indicates: NO.
However, VNC does it. Windows RDP does it (when you provide your credentials). Is there any way to use these programs to unlock the current workstation on a predefined schedule without human intervention?
Providing a user account and proper credentials is not a problem, and we have ways to appropriately encrypt/decrypt our passwords so they are available to a shell script or programming system.