I used an iPhone boarding pass when flying JNB/CPT last week (on BA). No issues at security, lounge or on boarding. So the system seems to be working at JNB.

When I boarded the flight attendant who looked at my BP seemed slightly perplexed but didn't say anything. I thought she was either unfamiliar with electronic BPs or was having trouble reading it. Only when I got to my seat and wanted to turn my phone off did I realise that I had accidentally flashed an old BP for LHR/MRS!