Yes. An L-2 spouse is employment-authorized incident to status and may work for the affiliate, another employer or himself once admitted with an I-94 that identifies him as an L-1 spouse. Keep his role out of the L-1B justification, and note that L-2 children cannot work.
Independent work permission, kept separate from the petition
The grower's spouse and unmarried children under 21 are admitted in L-2 status alongside her. Under current USCIS policy the spouse's work authorization flows from status itself, so he can accept a position on arrival without first obtaining an employment authorization document, provided his admission record carries the spousal notation. The affiliate is free to employ him, but the L-1B petition should not depend on it: if the greenhouse's transfer plan needs both of them to succeed, an adjudicator may ask whether the specialized knowledge really belongs to one person.
Children may study in the United States in L-2 status but have no work authorization at any age until they hold a status of their own, and a child who turns 21 during the assignment ceases to qualify as a derivative on that birthday. Both spouses should keep their own employment records, since either may later seek a different category or an extension on independent facts.