"Evidence" is a misapprehension of the system. I don't need "evidence".
If you read the OW T&C carefully, including those for BAEC, you will see that avios are awarded for flying another OW carrier when the other carrier certifies the segments & miles to the awarding carrier.
Thus, in this matter, when EI certifies to BA.
As you can see if you parse this thread or if you were to submit for missing avios to BA where your flights were on another OW carrier not requiring a fax (example is
#7 ), the miles post based on use of an online form.
Pointless to argue with you.
If when OP pulls up the missing avios form his PNR involving EI, he is asked for a fax, it means that EI requires a fax. If he had flown QR, he would have pulled up an online form. It means that QR does not require a fax.
Do I have "evidence" beyond that? No.
Do I need "evidence" beyond that? No.
Will it help OP's situation to find such "evidence"? No
But, will EI really care if BA faxes over what is sent to BA as a PDF attachment? Doubtful unless EI uses forensics experts to parse the faxes. Unlikely and if it does, the worst OP faces is having to resubmit.