The sliding panels are visible by both the GM and the Players. However, when the left or right sliding panel opens, players only see information about the counties in which the assets are controlled by factions they have access to (via the security field on the Factions screen).
The left sliding panel only shows the Factions in the tree for the counties that are controlled by the faction of the player or the counties in which the assets are controlled by factions the player has access to.
The right sliding panel does not show anything in the three tabs of the table unless the selected county is controlled by the faction of the user or contains assets that are controlled by factions the player has access to.