Servos do not have Ghosts in regular gameplay. I guess machines do not have Souls. I haven't tested it in game, but could do so quickly...
So I downloaded a Servo and a Ghost Servo (hax!) from the Gallery to test and these are the results:
• Neither regular nor Ghost Servo have Soul's Journeys in their Aspiration panel. Ghost Servo does have the Ghost Powers available and their tombstone in their inventory (though it's the regular Sim one, not the Servo one, likely broken by cheating).
• Turned on Testing Cheats and CAS Full Edit Mode and took them into CAS to see if I could add/edit Death Traits. Not possible on either Servo.
• Tried adding Death by Drowning trait to Servo in Live Mode, via cheat bar. This works, second Ghost Servo also has Ghost powers, but still no Soul's Journey.
• Removed Ghost trait and tried in-game death via cheat (rabbit). Servo dies and leaves Servo Tombstone. No option to continue as a Ghost/be a free roaming Ghost. Just gone. This Servo left a Servo tombstone behind.
So it looks as though you can have Ghost Servos with Ghost powers via cheats, but they can't be made through CAS or gameplay and they never have Soul's Journey in any instance.