The IRS has posted Frequently Asked Questions relating to CARES Act Retirement Plan Provisions.
According to Q & A 7, a taxpayer who elects to repay a COVID-19 related distribution would pay the tax on the three-year schedule and then amend the tax returns and request refunds when the distribution is repaid.
According to Q & A 9, employers may optionally amend their retirement plans to permit loans and distributions permitted under the CARES Act, so some employers might not allow the increased loans and distributions.
Here is a URL for the FAQs. https://www.irs.gov/newsroom/coronavirus-related-relief-for-retirement-plans-and-iras-questions-and-answers