Oh, wow! I had no idea that these were all traditional bishops in the picture! Thank you for sharing that, Ladislaus! 
Now, I believe at the time of the picture, only Bishop Vezelis was a bishop. He had been consecrated by bishops Carmona and Zamora, who in turn had been consecrated by Archbishop Thuc. Then Bishop Vezelis consecrated Father Musey, with +Carmona and +Zamora as co-consecrators. Father McKenna was then consecrated by fellow Dominican Bishop Guerard des Lauriers, who in turn had been consecrated by +Thuc. Bishop McKenna then consecrated Father Vida Elmer.
So the priests here say that they only realized later that they had all become bishops, and that these meetings were not about consecrations. Interestingly, these gatherings would have been an opportunity for them to get consecrated directly by Archbishop Thuc, but that wasn't their focus. In one sense, I kindof wish they had just directly been consecrated by +Thuc there, because (since we had 5-6 priests present), that would have undermined one of Bishop Kelly's narratives, namely, that there weren't "competent" witnesses to the consecrations of Guerard des Lauriers, Carmona, and Zamora (saying that the Germans Hiller and Heller did not "count").
Of course, Bishop Kelly made that canonical requirement up out of thin air. Not only did the Church accept 100% secret (aka unwitnessed) consecrations, but the Church in some cases ordered them to remain secret ... behind the Iron Curtain, and NOWHERE in Canon Law are witnesses required to attest "I witness that the matter and form were properly performed" but only that the consecration took place. It's presumed that a properly-trained Bishop validly performed the consecration. Archbishop Thuc held 3 Doctorates (when they actually mean something and you had to be very proficient in Latin to get these degrees), founded/started a seminary, and he performed 6 episcopal consecrations before Vatican II and was a co-consecrator of 9 more ... so he was thoroughly acquainted with the Rites. Not to mention, when then-Father Sanborn went to visit Bishop de Castro Mayer, seeking a consecration, the Bishop told them to go to Bishop des Lauriers. When Father Sanborn raised his concerns about the consecration, Bishop de Castro Mayer chuckled and said that if there's anyone competent to know whether a consecration was valid, it was "Guerard" (arguably the top theologian in the Church prior to Vatican II, having helped with the Dogma of the Assumption, served as personal confessor to Pius XII for some years, and latter having been the primary author of the Ottaviani Intervention). Bishop Carmona was also a seminary professor before Vatican II (when again it meant something and you had to be well trained and very fluent in Latin).
So there's no positive doubt whatsoever regarding the validity of the consecrations of Bishops des Laurier, Carmona, or Zamora. Nor, ironically, for the ones that +Thuc performed for the Palmar group (which was extremely public, witnessed by hundreds, and assisted by a seminary professor from Econe). Now some of the other lines are sketchy. If look at Boyle's list of Thuc consecrations/ordinations online, there are probably a dozen or more that are "disputed", where the consecrand claimed to have been consecrated by +Thuc but has no evidence, and in some cases +Thuc explicitly denied it. For some reason, it became fashionable among certain Old Catholic groups to just claim consecration by +Thuc to legitimize them.
Also, there's no evidence whatsoever that +Thuc was "out of his mind" and "senile". There's much eyewitness testimony that he was completely in possession of his faculties at least until the time he was kidnapped by the Conciliar Vietnamese. Not to mention that the bar is very low for the mental capacity required to validly consecrate. +Thuc merely needed to know what a consecration is and intend to do it. While +Thuc made some errors in judgment, that doesn't come close to the standard for being too mentally impaired to consecrate validly. And much of the allegations rest on the various consecrations that were falsely attributed to him. As for the Palmar thing, it was a seminary professor from Econe who roped +Thuc into that, a seminary professor who was directed to +Thuc by +Lefebvre for the request, when the latter said he was too busy. +Lefebvre had actually asked +Thuc to run the seminary at Econe, due to his experience having started them up from scratch, but +Thuc declined due to his age and health. And if having believed in a false apparition makes one incapable of validly consecrating, then that could eliminate Bishop Williamson as well ... but of course we know that Bishop Williamson remains in full possession of his faculties, despite some (IMO) errors in judgement.
But the main lines in the US are undoubtedly valid.
+des Lauriers -> +McKenna -> +Sanborn (+Selway, etc.)
+des Lauriers -> +McKenna -> +Neville
+Carmona -> +Pivarunas (CMRI)
+Carmona -> +Pivarunas -> +Dolan (SGG bishops)