This is not only going to result in a lot of jockeying for authority in the classroom, it is very unfair to the rest of the students because their course experience is going to be dominated by T.'s constant attention-seeking and attempts to make himself 'stand out' from the rest in the most tiresome way possible.
It is interesting that Tammy reports T, asking her "Dr. Tammy, What do you think?" but doesn't report her response. Did she not respond? In fact, the student whom T. interrupted, a student who was supposed to be the focus of class attention, quickly fades from focus, and Tammy's assessment of the quality of that student's paper is absent. This is T.'s strategy: to always return the focus back to him, ultimately at the expense of his peers.
Tammy was probably so gobsmacked by T.'s comment that she couldn't think of appropriate response to "rein him in" in that very moment, but now that Tammy knows his M.O., she needs to nip it in the bud next time. Something simple like "Please do not interrupt A. until she has finished reading her whole paragraph," might work, followed by a meeting during office hours to communicate to T. that continued outbursts of that nature will not be tolerated.
Tammy might want to add that there is simply not enough time in one class session for him to respond to each and every comment made by her and the other students, so he will of course understand if she doesn't call on him, or interrupts him to call on someone else if he tries to do this repeatedly.
As for the cosy after-class discussions, just walk away. No it is not good that he is so involved, because the class is becoming all about him. This is about him manipulating the situation so that he can become the center of attention, just as he was to his mother or father or whoever home schooled him. He needs to learn that there are other people in the classroom who are there to learn as well, and that he has to share both the time and space of the class with those students.