A company will add an HSA option mid year. I don't know yet if this will be inside or outside their 125 plan.

The main question being asked is can this trigger a change of election wherein and employee drops their FSA in favor of the HSA. I say it does not.

My own question is can (or what's the use of) an employee have both an HSA election and an FSA. election?

I do not think that the addition of contributions-to-HSAs in the middle of a plan year allows the employee who already has elected an FSA for the year to stop that FSA election mid-plan year.

An employee may have both an FSA and contributions-to-HSA elections, provided that the FSA is limited to preventive care or has a deductible that makes it HDHP coverage so that the employee is eligible for contributions to an HSA. Such a limited FSA yet provides tax-free reimbursement of certain medical expenses incurred in the plan year for which the limited FSA is elected, while the contributions to an HSA can create or add to a fund that is available for payment for other current plan year health expenses or health care expenses incurred after the plan year has ended.