Controlled group & successor plan

[Trekker]

Basic Facts: Parent Company A owns Company B. Company B has no employees. Company A has employees and maintains a 401(k) plan.

On October 1, 2006, an unrelated party is buying the stock of Company B. After the sale, the new buyer will hire some employees from Company A. The new owner wants to establish a safe harbor 401(k) plan for these employees effective October 1, 2006. It would be a calendar year plan.

Before the sale, even though Company B had no employees, it was part of a controlled group that did have employees.

The final regs say: A plan is a successor plan if 50% or more of the eligible employees for the first plan year (10-1-06) were eligible employees under a CODA maintained by the employer in the prior year.

For the successor plan rules, before the sale, is Company B considered an employer maintaining Company A's plan?

Any cites would be helpful.

Thanks in advance.