The Daily Journal of Commerce reports that the PREM group is planning to use the Custom House for meeting rooms and also as an "incubation space for nonprofits." That could be exciting—there's a couple large buildings in town that offer flexible, relatively cheap, subdivided space for little nonprofits.
The Custom House has been somewhat of a burden on the federal government, which has been trying to sell the behemoth for about six years. Last year, the Department of Education gave the Custom House to a local private school for free. But the school eventually backed out of the deal that would have required $8-10 million in repair work to bring the Custom House up to earthquake and disability standards.