Depends on the particular model/generation of Plextor drive.
Some of the oldest Plextor drives couldn't scan.
The PX-708/712/716/755/760/Premium/Premium2 can scan using the official PlexTools or the unofficial PxScan/PxView as well as QpxTool.
Some newer Plextor drives made by LiteOn can scan using PlexUTILITIES.
Some Plextor drives can scan using Opti Drive Control (not free).
Some newer Plextor drives cannot be used for scanning AFAIK.