So my buddy called the disability line and according to him it was a mixed bag.
The agent (he did not comment on their accent or lack their of this time) first said that she is powerless to do anything with Basic Economy, but after my buddy referenced the info above, she said that she had to get a Supervisor to assist.
The Supervisor first admonished my buddy for buying a Basic Economy and said that she is sick and tired folks buying Basic Economy only to call and ask for essentially a regular economy ticket. After admonishing him, she asked about his disability and he explained that he is essentially wheelchair bound and will need the aisle chair to get down the aisle to his seat and a movable arm rest would be a plus.
He understands that this his wife cannot sit next to him and that is fine, once he is in hit seat, he can manage just fine, the agent said that he can bring his wheelchair the gate as always and that they will help him transfer to an aisle chair and at which point the baggage handlers will take his wheelchair and place it under the plane (as is usual).
She further explained that he will board early (which is normal for him) to accommodate the transfer to the aisle chair and any assistance in getting to his seat. She said that essentially the Basic Economy restrictions of boarding in Group 5 will not apply to him. She advised my buddy that he should let the Gate Agent know as well, so that she could facilitate the early boarding. She then assigned him an ADA seat and placed his wife next to him (which she added that she did not have to do) and he thanked her for that.
Lastly, she added that technically he is entitled to a small personal item only, but that in practice she did not know since he was boarding early if that would be enforced or not.
He said, if need be, we will pay to check our bags, such is life, he thanked for her time and that was that.
As he said to me, I could have lived without the snark, but beyond that UNITED did what is right, so he was happy.