In Chullin 14a, we have this:
מַתְנִי׳ הַשּׁוֹחֵט בְּשַׁבָּת וּבְיוֹם הַכִּיפּוּרִים, אַף עַל פִּי שֶׁמִּתְחַיֵּיב בְּנַפְשׁוֹ – שְׁחִיטָתוֹ כְּשֵׁרָה.
MISHNA: In the case of one who slaughters an animal on Shabbat or on Yom Kippur, although he is liable to receive the death penalty, his slaughter is valid.
גְּמָ׳ אָמַר רַב הוּנָא, דָּרַשׁ חִיָּיא בַּר רַב מִשְּׁמֵיהּ דְּרַב: אֲסוּרָה בַּאֲכִילָה לְיוֹמָא, וְנָסְבִין חַבְרַיָּא לְמֵימַר רַבִּי יְהוּדָה הִיא.
GEMARA: Rav Huna says that Ḥiyya bar Rav taught in the name of Rav: If one slaughtered an animal on Shabbat and Yom Kippur, although the slaughter is valid, consumption of the animal is prohibited for that day, and the members of the company of Sages, i.e., those in the academy, tended to say that this halakha is the opinion of Rabbi Yehuda.
Thus,
Rav Huna brings it into scope by quoting Chiya bar Rav, namely Rav’s actual son.
Chiya bar Rav is lecturing, darash, which implies something in a public statement.
The chavraya, meaning fellows or colleagues make a statement on top of Rav’s statement, as to how to interpret it.
My assumption is that the nasvin Chavraya is something that Rav Huna related, about a reaction to Chiya bar Rav’s quotation of his father, in that public lecture, in Sura academy. I would guess that this public lecture occurred after Rav’s death. (Alternatively, we might kvetch it to mean that Chiya bar Rav related the reception to Rav’s statement, but did not elaborate.)
Rav Huna (and Rav) is the Suran academy. The continuation of the sugya in the gemara, in which Amoraim discuss the meaning of Rav Huna’s statement about how the chavraya weighed in — to which statement of Rabbi Yehuda did they refer? — seems like it is Amoraim in the orbit of Pumbdita.
Tosafot are troubled by Rav Huna quoting Chiya bar Rav:
אמר רב הונא דרש חייא בר רב משמיה כו’ - תימה דבכל דוכתי משמע דרב הונא היה גדול ממנו בפ’ יש בערכין (ערכין דף טז:) דהוה מצער ליה רב הונא לחייא בר רב ובפ’ הלוקח בהמה (בכורות דף כב.) דא”ל חייא בר רב לרב הונא רבי פרש את דבריך:
After all, in all places, it seems that Rav Huna was greater (or of greater stature) then Rav. Tosafot give an example from Arachin 16b:
הֵיכִי דָּמֵי תּוֹכֵחָה לִשְׁמָהּ וַעֲנָוָה שֶׁלֹּא לִשְׁמָהּ? כִּי הָא דְּרַב הוּנָא וְחִיָּיא בַּר רַב הֲווֹ יָתְבִי קַמֵּיהּ דִּשְׁמוּאֵל, אֲמַר לֵיהּ חִיָּיא בַּר רַב: חֲזִי מָר דְּקָא מְצַעַר לִי. קַבֵּיל עֲלֵיהּ דְּתוּ לָא מְצַעַר לֵיהּ. בָּתַר דְּנָפֵיק, אֲמַר לֵיהּ: הָכִי וְהָכִי קָא עָבֵיד. אֲמַר לֵיהּ: אַמַּאי לָא אֲמַרְתְּ לֵיהּ בְּאַנְפֵּיהּ? אֲמַר לֵיהּ: חַס לִי דְּלִיכְּסִיף זַרְעֵיהּ דְּרַב עַל יְדַאי!
The Gemara asks: What is considered rebuke for its own sake and humility not for its own sake? The Gemara answers: It is like this incident that occurred when Rav Huna and Ḥiyya bar Rav were sitting before Shmuel. Ḥiyya bar Rav said to Shmuel: See, Master, that Rav Huna is afflicting me. Rav Huna accepted upon himself that he would not afflict Ḥiyya bar Rav anymore. After Ḥiyya bar Rav left, Rav Huna said to Shmuel: Ḥiyya bar Rav did such-and-such to me, and therefore I was in the right to cause him distress. Shmuel said to him: Why did you not say this in his presence? Rav Huna said to him: Heaven forbid that the son of Rav should be humiliated because of me. This provides an example of rebuke for its own sake, as Rav Huna originally rebuked Ḥiyya bar Rav only when Shmuel was not present, and of humility not for its own sake, as Rav Huna did not forgive Ḥiyya bar Rav but simply did not wish to humiliate him.
Tangentially, I would guess that this incident happened after Rav’s death.
Tosafot also point to Bechorot 22a:
תְּנַן הָתָם: אֵין לִנְפָלִים פְּתִיחַת הַקֶּבֶר, עַד שֶׁיַּעֲגִילוּ רֹאשׁ כְּפִיקָּה. מַאי כְּפִיקָּה? אָמַר רַב הוּנָא: כְּפִיקָּה שֶׁל צֶמֶר. אֲמַר לֵיהּ חִיָּיא בַּר רַב לְרַב הוּנָא: רַבִּי, פָּרֵישׁ שֶׁל שְׁתִי אוֹ שֶׁל עֵרֶב?
§ The Gemara continues discussing the ritual impurity imparted by a fetus. We learned in a mishna elsewhere (Oholot 7:4): If a fetus dies in its mother’s womb, it imparts ritual impurity from when the womb opens. Yet deceased fetuses do not impart ritual impurity in this manner even during the opening of the womb, until the head of the fetus is round like the size of a skein [pika] of yarn. The Gemara asks: What is the meaning of: Like a skein? Rav Huna said: It means like a skein of woolen yarn. Ḥiyya bar Rav said to Rav Huna: My teacher, explain your statement: Were you referring to a skein of warp threads or a skein of the thicker woof threads?
So we see that Chiya bar Rav called Rav Huna “my teacher”.
Despite this, this is no great surprise. Rav Huna, as a student of Rav, was privy to many statements of Rav. Chiya bar Rav, as student and son of Rav, might have been privy to other statements. Rav Huna was citing an incident in which Chiya bar Rav lectured, and the students of the time reacted. Why should Rav Huna not relate this incident? It is not the same as X quotes Y at all, which is how one related to a teacher. It is X quotes Y about what mutual teacher Z said, plus how parallel people A reacted.