BOA were on Atco records for their most commercial period. This catalog was not a part of Capricorn, and did not move to Universal with the rest of that label's catalog. I also doubt that Warner's spun off these BOA masters, but they likely reverted back to the band after 30 years or so. But UMG was not where these albums (included quad mix) ended up afaik.
The rights were sold to a label called RT Industries (ex-Razor & Tie execs) as part of Warner's divestment of the Parlophone catalog to independent labels.