Hi, Joel--thank you for engaging with my post! These are all great questions.
I only started my Ph.D. program about two weeks ago, so I sadly don't yet have any published research. (I'm hoping experiences like this one will help me change that!)
There are certainly people that are experts in these topics at MIT (e.g., Caspar Hare). However, for any grad program that I could've chosen, there would've been at most a couple of people focusing on these questions. Therefore, the decision to choose MIT was based not only on how many people would be able to help me with my research on this particular topic, but also other considerations that are important for my academic career (e.g., placement record). MIT seemed like the optimal decision. Nonetheless, I am still interested in getting to engage with more experts on these topics--I don't think I'd get very far in academia if I didn't try to collaborate with people outside of my department, regardless of what program I had chosen. Moreover, global priorities research is a broad field, with many interesting questions and perspectives. Working with faculty members at ANU would help me come up with new research ideas while getting new perspectives on topics that I'm already thinking about (for example, the possibility of imprecise credences and its influence on decision-making).
In terms of short-term outcomes for this trip, I think one hugely beneficial outcome would be just making lasting connections outside of my department. Many of my former professors have recommended that I visit other departments for extended periods (e.g., a summer, or a semester) before I go on the job market. If I succeed in the job market, then it'll be more likely that I'll be able to continue focusing on global priorities research. (And, given how neglected this career path is, I expect that this could be beneficial for the world.) More importantly, and as I mentioned above, I also hope to come up with new research ideas during this trip and eventually publish them. In particular, I hope to work with Alan Hájek (he's one of the faculty members I've already reached out to), who has recently published papers like “Degrees of Commensurability and the Repugnant Conclusion" and “Non-Measurability, Imprecise Credences, and Imprecise Chances." These are already topics that I'm working on at MIT (with Caspar Hare and Kevin Dorst), and which have important implications for decision theory and population ethics.
Let me know if that answers your questions--if not, I'm happy to provide any more details that would be helpful!