In the morning at 7 clock Fr Jasny "could" celebrate the Mass in St. Peter’s - the report on the website of the SSPX states- at "that mysterious, quiet time of daybreak in St. Peter's, before the arrival of the torrents of tourist."
The paleo- liberal Swiss news agency 'Kipa-Apic' complained about the Latin Masses in Rome.
The person responsible for arranging Masses in St. Peter's said that there was no written request from the Father for the period concerned.
But it is possible that a priest can ask in the sacristy directly for an opportunity for celebration. Whoever presenting evidence of priesthood and asking for a Missal for the traditional rite, does not get a negative response.