Affiliated Service Group & ERISA

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So, there is a segment of a business that that is being spun-off and a new company will be the employer.  The employees in the new company are being transferred from the old one as part of the transaction.  The business selling off will retain 9.9% ownership in the new company and an affiliated service group relationship will exist post sale.  

Is itt true that companies in the same service group may be treated as a single employer under the Code (409A) but not as a single employer under ERISA?  Meaning no termination of employment under the qualified plans or health plans?