Is it forbidden or problematic for a husband to introduce his friend, who owns an elevator company, to employees from competitor companies of his friend?

The Prophet, peace and blessings be upon him, forbade a Muslim from selling over the sale of his brother, and leasing has the same حكم as selling. Therefore, your husband's friend's offer to employees of competing companies to leave their jobs during their contract period and join him falls under this prohibition. If your husband gives him their phone numbers for this purpose, he would be assisting in sin and aggression, and Allah Almighty says: "And do not cooperate in sin and aggression."