Not sure if this rc track finder is up to date, but you could give it a try:
http://www.rc-strecken.de/?s=schwerin
Other than that, I've heard good things about the Burgdorf on-road and off-road tracks, and mixed opinions on the RC Glashaus in Hamburg/Quickborn, which is an indoor track. I haven't been at any of those facilities as they are not exactly nearby.