Here is some additional information:
Here you can see two SSTV transmissions starting at about 150s. I see no impact on the ongoing qso's going on higher up the passband.
Here there is an SSTV transmission at about 200s, also doesn't seem to impact the ongoing qsos.
And yes - all of this was in SSB. I suppose a trial in NFM would really cause havoc on the transponder.