According to this quote by Kenneth Roy Norman that I found on the Atthakata page in Wikipedia:
There is no direct evidence that any commentarial material was in fact recited at the first council, but there is clear evidence that some parts of the commentaries are very old, perhaps even going back to the time of the Buddha, because they afford parallels with texts which are regarded as canonical by other sects, and must therefore pre-date the schisms between the sects. As has already been noted, some canonical texts include commentarial passages, while the existence of the Old Commentary in the Vinaya-pitaka and the canonical status of the Niddesa prove that some sort of exegesis was felt to be needed at a very early stage of Buddhism.
If this is true then which material from the Theravada/Vibhajyavada commentaries is shared with which parallels from other sects? (I assume these are EBTs)
From this is it possible to know if these sects also developed their own commentaries on the Nikayas/Vinaya? And if so then in what way? In terms of language? composition? content?