The ACC just put the Men's Basketball Tournament for 2016-2021 out to bid this past summer, and neither Madison Square Garden nor the Brooklyn Barclays Center submitted a bid. So the Men's Basketball tournament can't be in MSG until at the earliest 2022, and to do that MSG at least has to submit a bid for the tournament.
Atlanta, Charlotte, and Greensboro all submitted bids. I'm not sure who else did. The Tournament is locked into Greensboro for 2013-1015. The ACC has been evaluating the bids for 2016-2021, but I haven't seen an announcement. It's been in Tampa, FL and Washington, DC before. I don't know if those cities placed bids this time. The bid involves not only the venue, but it also involves hotels bidding. The ACC tournament has now been extended to 5 days.
New York is going to need to bid on the ACC tournament if it's going to be held there. MSG has the Big East tournament through 2016. It's trying to bid on extending that. I'm not sure what will be left of the Big East Tournament by 2016.