I have Nokia mate, I think the app is reading the data from the eMMC and you will have to modifying the configure file somewhere in the home folder.
But OVI map on N900 suck hard time. Not much you can do with it at the moment. GPS took like 1hour to lock without connection on a cold start. You will have to run the Locate app to work. I'm hoping they would fix it and add more functionality like off line search.