N.J. Stat. § 48:2-37
The board, or any member of the board, may compel by service of its subpoena the production of the books, accounts, records, contracts and other documents in writing of (a) any corporation or person owning, holding or controlling, separately or in affiliation with another corporation or person, five per cent or more of the capital stock of any public utility, and of (b) any corporation five per cent of whose capital stock is owned, held, or controlled by any corporation or person so owning, holding or controlling, separately or in affiliation with another corporation, or person, five per cent or more of the capital stock of any public utility, respecting any relation between such public utility and such corporation or person.
The board, or any member of the board, may compel the attendance of witnesses for the purpose of obtaining information as to such books, accounts, records, contracts, and other documents and writings in the same manner that witnesses are now compelled to testify before the board.
Information, books, accounts, records, contracts and other documents in writing obtained by the board through the proceeding hereby authorized shall be used by the board only for the purpose of aiding the board in reaching a determination in a proceeding or on an issue before it, and for no other purpose.
N.J.S. § 48:2-37