Hmm ... doesn't work like that. You have to setup a proxy like Gnuite did (i did for both gmaps and maps.live.com - only the first still working ... cause MS changed the format it encodes the polyline), then you ask for a direction (have to make fake a browser call, fetch the polyline, - figure out the algorithm, get the gpx data )

You cannot get a vectorial map, you will end-up requesting routes from your server every time you need one

pm me if you need help

PS: i really don't think abusing gmaps is a good ideea ... hope they will not change the format like VEMaps did ( aka M$ )

Cheers
Mihai