I recently had a trip to Seattle ticketed by AA prior to the October change. The outbound segments were cancelled and re-arranged twice last December, with completely new segments two days later than originally ticketed. On the inbounds, an AA segment to LHR was then cancelled at the gate, and I re-routed with BA the following day. All segments posted correctly (including uplifted BA segments that received, by my reckoning, Avios at the pre-October rate). Only one outbound AA segment did not credit automatically, which was rectified by uploading a photo of one of the outbound paper tickets, which were issued at T3 connections and the first paper tickets I've received in years. TPs and Avios were credited by BA about 48 hours later, and although about 1,000 Avios short (by my reckoning) I was content all round.

And certainly a bit quicker than having to a) fax a copy to BA and b) trying to find a fax machine in my village (which surprisingly I did find at the local Italian restaurant of all places), which happened when a few Royal Jordanian segments did not credit in 2016. The last time I had used a fax machine prior to then was about 20 years earlier. :-)