Only way for you to know is to ask your doctor about it. It wasn't something my PM "offered" to me. I had to ask.
In Illinois, you're supposed to see your doc every month if you're on C2's, but I can still get a script for 90-day mail order. I just need to continue scheduling monthly appointments with my doc, but it does save me a lot of money on filling the script (plus no chasing down medications all over creation). It is a lot of medication so not all doctors are comfortable writing for a 90-day supply and even those that are okay with it for some patients might not allow it for others. It wasn't clear to me from your post, but you do understand that the 90-day service is offered by your prescription insurer, not your doctor, right? You PM would just write a script the same as if it were a monthly refill & you would have to send it off to your prescription insurer to fill. Not all insurance companies offer this service, so be sure to check with them before getting a script from your doc.