FWIW, I was admitted into the AC at SFO on a "paid A" RTW ticket, flying SFO-JFK last spring. No questions or funny looks from the receptionist. Maybe I got lucky.
I was prepared to go to the mat irrespective of the "official" admit policies ("I spent $10,000 on this stinkin' ticket and I can't even sit in this lounge where I have to buy my own booze anyway?!?"), but didn't need to. Of course I probably didn't realize at the time that the revenue AA gets on that segment from that ticket is significantly less than $10K.

So, YMMV.

BTW, I have to think that the lack of official access on AONE* fares is probably just an unfortunate byproduct of them booking into the same inventory class as mileage upgrades, some YUPs (on 2-class JFK-SFO) and DONE* fares on 2-class, and a desire to have "simplified" lounge admit policies. I would like to think that it should be AA policy to admit AONE* travelers into the AC/FL, if they're willing to admit award tickets. But I could be wrong.