Our cottage is in Honey Harbour, not too far away from Port Carling. I would say you'll have better luck the closer you get to Parry Sound. Having said that, we were supposed to get 15-20 cm at the cottage this week, so conditions may have improved. Check out
MSR it's the Muskoka Snowmobile Region website. Click on the trail conditions link. As far as Parry Sound goes, I can't quite remember, their site might be ParrySoundSnowmobile.com. Can't say for sure. Best of luck & have fun!