My company has a policy (that HR has made very, very clear can be changed at any time) where for RSUs that are vesting, the company will pay the income taxes for the employee in exchange for withholding/essentially buying back a portion of the vested shares (the exact mechanism by which this is done isn't something I really looked into).
This policy opens up a backdoor way of essentially liquidating my vesting shares: I can simply file a new withholding form just before the vesting date, claim way fewer tax exemptions, and the company will withhold a higher portion of the vesting shares/remit more cash to the tax authorities. Upon filing my tax returns at the end of the year, I can receive the excess cash remitted as a refund.