First of all I should mention the Ovi API are being deprecated I strongly urge to switch to Nokia Maps API (api.maps.nokia.com). Ovi was rebranded to Nokia and the signatures of the APIs are quite similar so switching should be easy and you will heat maps, places, KML and mobile support as a bonus (see for list of examples
http://api.maps.nokia.com/en/playground/env/nojs/).
To answer your question of determining intersection between a marker and a route, I think map.getObjectsAt is the best method to determine this.
Have a look at this example
http://api.maps.nokia.com/en/playgro.../tracking.html
Don't have time tonight but I will try to write you an example tomorrow..