Medicare Advantage Retiree Medical Plan - Avoidance of Doughnut Hole

[rocknrolls2]

I participate as a retiree in my former employer's retiree medical plan, which is a Medicare Advantage PPO. As such, it includes Part D for prescription drugs, including the doughnut hole. I know that the ACA had provisions designed to ameliorate the doughnut hole.  I was informed that I could not enroll in any other medicare supplement plan (including for prescription drugs) or I would lose my coverage. I therefore have the following questions: (1) were the ACA provisions which were intended to lessen the impact of the doughnut hole ever implemented or put into effect? (2) if (1) is yes, are they still in effect? (3) If (1) or (2) is No, can my former employer design the prescription drug portion so as to lessen the severity of the doughnut hole provision?

Thank you!