Shiv2016, the present perfect gives us information about the actual action in that tense, so it applies to the words "has stated." That doesn't tell us anything about whether what was stated continues to be true. Consider these:
I said that I was married.
I said that I am married.
I have said that I am married.
In the first case, the action ("said") is in the past. At some point in the past, I said that I was married. This says nothing about whether I am married now, but it doesn't preclude my being so. In other words, using the past tense doesn't mean that I have stopped being married! It just tells you about when I said what I said.
The second sentence makes it clear that I am married now. The action of speaking is in the past, but I would only use this form if the action had happened very recently. It would not work to say "When I started this job 20 years ago, I said that I am married."
The third sentence implies that I have referred to being married before, perhaps repeatedly, and that this reflects the current state of things. However, this is no more "correct" for showing that I am still married now than sentence two is.
A shorter answer is that we have to pick. We can use "at a recent conference" or "has stated," but not both. Any sentence that starts with "At a recent conference, the transit authority has stated" can be ruled out without any need to read further.