Is this an HMO? I signed up for one once and the delays were pretty stupid (even to get a referral to a specialist you needed to come back to see a different doctor first). I've never signed up for the HMO plan again since. With a PPO you can always pick another specialist that is available.
Meanwhile there are companies in Canada that help Canadians get their MRI's in the US because it's so slow there. And clinics near the border advertise in Canada.