Can borrower proceeds from the sale of tax credits for the subject property count toward borrower’s 15% contributed capital requirement when determining whether a loan is classified as HVCRE or not?

I think the closest you are going to fine is this, but it going to be worth visiting with your regulator:

11. Projects may receive cash in the form of grants from nonprofit organizations, municipalities, state agencies, or federal agencies. Can a banking organization providing ADC financing to a project (that does not otherwise qualify as a community development investment with regard to the HVCRE exemption) consider the cash from such grants as part of the 15 percent contributed capital requirement?

No, to the extent a project receives a grant, a banking organization may not consider the cash from the grant as a capital contribution because the cash did not come from the borrower. Although a third-party grant would increase the capital invested in the project, because it does not come from the borrower, it does not affect the borrower’s level of investment and therefore does not ensure that the borrower maintains a sufficient economic interest in the project.