I understand that the Map is already known to the robot.
lidarSlam object helps in building the Map by performing localization and mapping using the lidar scans. Hence lidarSlam will not be of use here.
If the map of the environment is already known to the robot, robot can do localization by the help of localization algorithms like Monte carlo localization.
Refer the Estimate Vehicle Pose from Range Sensor Data section in the following example that uses Monte Carlo Localization for robot pose estimation. This method require a couple of scans taken in succession for effective localization.