I’m also not sure what the question means here, are you trying to ask if someone has used T5 for classification ?Then  yes, I’ve fine-tuned it for both binary and multi-class classification here 181.
As for measuring the probability, this paper 41 used T5 in really interesting way for document ranking. First they train the model to predict true if   doc is related to the query and false if not. And for ranking they apply a softmax only on the logits of the “true” and “false” token and rerank using the probabilities assigned to the “true” token.
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