ILLINOIS TRS HEALTH INSURANCE

I read one of Terry‘s articles about advantage plans not being a good thing for people who need a lot of medical attention. I am a retired educator and the Illinois TRS system offers what they call a PPO advantage plan through Aetna. Is this one of the advantage plans that is negotiated by the union and corporation and is different than other advantage plans open to the general public? She has said that these advantage plans are not on the same level as a general advantage plan through Medicare . please advise. Thank you.