Mid-year election change - carrier change at spouse employer

[jsb]

Employer A changes insurance providers mid-year and transfers ALL enrollees to a new plan. Old health plan is a multi-provider standard HMO, new health plan is a closed panel HMO HDHP. They do not offer a special enrollment window for their employees to make an election change. If we had made a similar change, we would have allowed an open enrollment window based on a significant change in coverage.

My employee's spouse works for Employer A, and would like to make an election change to add his wife to his plan. His cost of adding her to his non-HDHP HMO coverage with the same carrier would be much less than the upcoming Dr. visit and maintenance prescriptions costs she will incur under her new HDHP.

Has a "loss of other employer's coverage" occurred which would constitute a Qualifying Event as respects our plan? While the spouse had an involuntary change of health plans, she did not actually lose employer sponsored coverage, it just changed dramatically.

Your thought appreciated.