On topic, I have just found this on the Campos Administration website.
Google translation from Portuguese:
"Note, however, that in the time of Dom Antônio's episcopate, who preferred and celebrated the Mass in the old rite, from 1969 (when the New Mass was promulgated) until 1981 (when Dom Antônio became emeritus), there was in the diocese of Campos, parishes and churches where the Mass of Saint Pius V was celebrated, alongside parishes and churches where the Mass of Paul VI was celebrated, with the permission of the Diocesan Bishop, who preserved, and even appointed as parish priests, priests who only celebrated in the new rite."
Modernists are often also big liars, but if this is true, it speaks a lot in disfavour of Bp. Castro Mayer.