If you need to be referred, you can only chose from a short list of CityMD approved partners. This means you have very limited choice of which doctor you can receive treatment from.
For example:
CityMD Dr diagnoses you with problem X.
They offer to refer you to Dr Y - who is not good.
You ask for the referral letter so you can choose your own Dr Y.
CityMD WILL REFUSE TO GIVE YOU YOUR REFERRAL!
= SHADY!
Avoid.