I believe that the fact that the company is changing health care providers should have no affect on your eligibility of COBRA - see these related questions:
Q12: Under COBRA, what benefits must
be covered? Qualified beneficiaries
must be offered coverage identical to
that available to similarly situated
beneficiaries who are not receiving
COBRA coverage under the plan
(generally, the same coverage that the
qualified beneficiary had immediately
before qualifying for continuation
coverage). A change in the benefits
under the plan for the active
employees will also apply to qualified
beneficiaries. Qualified beneficiaries
must be allowed to make the same
choices given to non-COBRA
beneficiaries under the plan, such as
during periods of open enrollment by
the plan.
Here's more supporting evidence:
Q24: Am I eligible for COBRA if my
company closed or went bankrupt and
there is no health plan? If there is
no longer a health plan, there is no
COBRA coverage available. If, however,
there is another plan offered by the
company, you may be covered under that
plan. Union members who are covered by
a collective bargaining agreement that
provides for a medical plan also may
be entitled to continued coverage.
From the department of labor website.
The reduction of hours should also be considered a qualifying event.
Qualifying Events for Employees:
- Voluntary or involuntary termination of employment for reasons
other than gross misconduct
- Reduction in the number of hours of employment