Impact of Spin Off on existing stock grants?

When a company spins off or divest a division, this can often negatively impact the stock price. The shareholders of the current company, which includes any employees with shares, may get stock in the spin off of the new company.

But what about employees that have outstanding stock options or restricted stock, or an ongoing ESPP offering period, is there any adjustment , such as in the exercise/purchase price or size of the grant? How do most stock plans handle this situation?

Thanks for your input.

Bruce