Hello.

Is it possible to open screen lock programmatically? ie. from another program.

I know how to prevent system from enabling it. But the problem is that once the lock is activated, this dbus call doesn't do anything. So i'm guessing that there might be some other call for this.

The official answer is no, because of security of the device there is no way to open the screen lock programmatically.

With exploited capas answer might be different, but that you will have to figure out yourself.

Really? I mean just opening the screen lock.
(not the device lock where you have to enter password)

Killing sysuid at least does the trick, but it's a bit too ugly solution. :-)