HR due diligence – On ESOP

Dear fellow coursemates,

Does someone have some experiences about the treatment of Employee Stock Ownership Plan (ESOP) of the acquisition target?

Say if the acqusition target has some outstanding ESOP and some of the shares are still not vested yet, how are the unvested ESOP shares typically treated when the acquisition happens? Will the unvested ESOP directly turn vested at the completion of acquisition or just simply cancelled?

Thank you.