There are two types:
1. For the older versions, VTR Types, Ball bearings were used both the sides, having a small gear pump and an oil bath for lubrication. This is common now also.
2. In the MET Types, which is the latest design, Shell type white metal bearing is used in the centre of the shaft. The lubrication is by the main system itself and there is a header connection also for the lub oil to flow when the Engine is stopped/Lub oil pump stopped. The thrust Bearings for both sides are slotted bearings and the replacement criteria for the same is the dye check and assesing the percentage area of contact worn out for each slot. These are the bearings in the turbocharger.