Yes. An L-2 spouse is employment-authorized incident to status and may work for the affiliate, for anyone else or for herself. Children in L-2 status may attend school but may not work.
The spouse's work follows her status, and her status follows his
Under current USCIS policy the spouse of an L-1 transferee holds employment authorization as a consequence of L-2 status, so she does not need a separate work permit before taking a job. She could keep the books for the U.S. greenhouse, join an accounting firm or continue serving Canadian clients from the United States, since the location of the work is now lawful for her.
Her authorization is derivative: it ends if the principal's L-1A ends, changes category or lapses, and it must be supported by her own valid admission record. Any professional credential she needs for U.S. bookkeeping or tax preparation is a separate state or federal matter.
Their children, admitted in L-2 status, may study at any level but hold no work authorization, and each child loses derivative status at twenty-one. Family members need not be Canadian citizens; only their relationship to the principal is tested.