There is a 100 year old post that says dolmus run from Iznik to Bursa, taking about an hour. Anybody know if that is still the case? More current information suggests that you have to take a bus to Orhangazi and then transfer to a bus to Bursa. I'm hoping to avoid that. Thanks!
In addition to any replies you get here, look at Turkey Travel Planner, which I found invaluable for my trip: http://turkeytravelplanner.com/
Each 30 min, there is direct bus between Iznik and Bursa. Do not worry about that. You do not need to book in advance either.
Thats the company operates buses but their website is on construction.