@JCitron:
The sessions for the PO&N map use 'navigate', and as a consequence I found that the AI trains were using the player-dedicated tracks when the tracks for AI trains were occupied, which can happen when the player enters one of the squeeze points thus blocking an oncoming AI train AND the interval between two AI trains is a bit narrow (10 minutes or less). For that reason I took to updating the session (thus making a new one) where I replaced all 'navigate' commands with 'drive'.
Dralex