This is not the case anymore since ~5 years. The only motorized vehicels alllowed are those that cant travel fasher than 25km/h (bike speed)
Amsterdam is also pushing very hard to get an exception to be able to force them onto the street though.
("Herinnering: <scooter icon> op rijbaan", example here: http://www.rotterdam.nl/Clusters/Stadsontwikkeling/Document%...)
Although I think that it's illegal for them to ride in the bike lanes (or over 25km/h? or both?), they still do it